--- a/devtools/server/actors/script.js
+++ b/devtools/server/actors/script.js
@@ -16,17 +16,16 @@ const { ObjectActor, createValueGrip, lo
 const { SourceActor, getSourceURL } = require("devtools/server/actors/source");
 const { DebuggerServer } = require("devtools/server/main");
 const { ActorClassWithSpec } = require("devtools/shared/protocol");
 const DevToolsUtils = require("devtools/shared/DevToolsUtils");
 const { assert, dumpn, update, fetch } = DevToolsUtils;
 const promise = require("promise");
 const PromiseDebugging = require("PromiseDebugging");
 const xpcInspector = require("xpcInspector");
-const ScriptStore = require("./utils/ScriptStore");
 const { DevToolsWorker } = require("devtools/shared/worker/worker");
 const object = require("sdk/util/object");
 const { threadSpec } = require("devtools/shared/specs/script");
 
 const { defer, resolve, reject, all } = promise;
 
 loader.lazyGetter(this, "Debugger", () => {
   let Debugger = require("Debugger");
@@ -489,24 +488,16 @@ const ThreadActor = ActorClassWithSpec(t
     if (!this._threadLifetimePool) {
       this._threadLifetimePool = new ActorPool(this.conn);
       this.conn.addActorPool(this._threadLifetimePool);
       this._threadLifetimePool.objectActors = new WeakMap();
     }
     return this._threadLifetimePool;
   },
 
-  get scripts() {
-    if (!this._scripts) {
-      this._scripts = new ScriptStore();
-      this._scripts.addScripts(this.dbg.findScripts());
-    }
-    return this._scripts;
-  },
-
   get sources() {
     return this._parent.sources;
   },
 
   get youngestFrame() {
     if (this.state != "paused") {
       return null;
     }
@@ -640,18 +631,16 @@ const ThreadActor = ActorClassWithSpec(t
     try {
       // Put ourselves in the paused state.
       let packet = this._paused();
       if (!packet) {
         return { error: "notAttached" };
       }
       packet.why = { type: "attached" };
 
-      this._restoreBreakpoints();
-
       // Send the response to the attach request now (rather than
       // returning it), because we're going to start a nested event loop
       // here.
       this.conn.send(packet);
 
       // Start a nested event loop.
       this._pushThreadPause();
 
@@ -1179,17 +1168,18 @@ const ThreadActor = ActorClassWithSpec(t
   _breakOnEnter: function (script) {
     let offsets = script.getAllOffsets();
     for (let line = 0, n = offsets.length; line < n; line++) {
       if (offsets[line]) {
         // N.B. Hidden breakpoints do not have an original location, and are not
         // stored in the breakpoint actor map.
         let actor = new BreakpointActor(this);
         this.threadLifetimePool.addActor(actor);
-        let scripts = this.scripts.getScriptsBySourceAndLine(script.source, line);
+
+        let scripts = this.dbg.findScripts({ source: script.source, line: line });
         let entryPoints = findEntryPointsForLine(scripts, line);
         setBreakpointAtEntryPoints(actor, entryPoints);
         this._hiddenBreakpoints.set(actor.actorID, actor);
         break;
       }
     }
   },
 
@@ -1313,17 +1303,18 @@ const ThreadActor = ActorClassWithSpec(t
   },
 
   /**
    * Get the script and source lists from the debugger.
    */
   _discoverSources: function () {
     // Only get one script per Debugger.Source.
     const sourcesToScripts = new Map();
-    const scripts = this.scripts.getAllScripts();
+    const scripts = this.dbg.findScripts();
+
     for (let i = 0, len = scripts.length; i < len; i++) {
       let s = scripts[i];
       if (s.source) {
         sourcesToScripts.set(s.source, s);
       }
     }
 
     return all([...sourcesToScripts.values()].map(script => {
@@ -1919,46 +1910,27 @@ const ThreadActor = ActorClassWithSpec(t
         from: this.actorID,
         type: name,
         source: source.form()
       });
     }
   },
 
   /**
-   * Restore any pre-existing breakpoints to the sources that we have access to.
-   */
-  _restoreBreakpoints: function () {
-    if (this.breakpointActorMap.size === 0) {
-      return;
-    }
-
-    for (let s of this.scripts.getSources()) {
-      this._addSource(s);
-    }
-  },
-
-  /**
    * Add the provided source to the server cache.
    *
    * @param aSource Debugger.Source
    *        The source that will be stored.
    * @returns true, if the source was added; false otherwise.
    */
   _addSource: function (aSource) {
     if (!this.sources.allowSource(aSource) || this._debuggerSourcesSeen.has(aSource)) {
       return false;
     }
 
-    // The scripts must be added to the ScriptStore before restoring
-    // breakpoints. If we try to add them to the ScriptStore any later, we can
-    // accidentally set a breakpoint in a top level script as a "closest match"
-    // because we wouldn't have added the child scripts to the ScriptStore yet.
-    this.scripts.addScripts(this.dbg.findScripts({ source: aSource }));
-
     let sourceActor = this.sources.createNonSourceMappedActor(aSource);
     let bpActors = [...this.breakpointActorMap.findActors()];
 
     if (this._options.useSourceMaps) {
       let promises = [];
 
       // Go ahead and establish the source actors for this script, which
       // fetches sourcemaps if available and sends onNewSource

--- a/devtools/server/actors/source.js
+++ b/devtools/server/actors/source.js
@@ -180,17 +180,16 @@ let SourceActor = ActorClassWithSpec(sou
 
   get isInlineSource() {
     return this._isInlineSource;
   },
 
   get threadActor() { return this._threadActor; },
   get sources() { return this._threadActor.sources; },
   get dbg() { return this.threadActor.dbg; },
-  get scripts() { return this.threadActor.scripts; },
   get source() { return this._source; },
   get generatedSource() { return this._generatedSource; },
   get breakpointActorMap() { return this.threadActor.breakpointActorMap; },
   get url() {
     if (this.source) {
       return getSourceURL(this.source, this.threadActor._parent.window);
     }
     return this._originalUrl;
@@ -439,17 +438,17 @@ let SourceActor = ActorClassWithSpec(sou
   /**
    * Extract all executable offsets from the given script
    * @param String url - extract offsets of the script with this url
    * @param Boolean onlyLine - will return only the line number
    * @return Set - Executable offsets/lines of the script
    **/
   getExecutableOffsets: function (source, onlyLine) {
     let offsets = new Set();
-    for (let s of this.threadActor.scripts.getScriptsBySource(source)) {
+    for (let s of this.dbg.findScripts({ source })) {
       for (let offset of s.getAllColumnOffsets()) {
         offsets.add(onlyLine ? offset.lineNumber : offset);
       }
     }
 
     return offsets;
   },
 
@@ -713,20 +712,27 @@ let SourceActor = ActorClassWithSpec(sou
     const { originalLocation } = actor;
     const { originalLine, originalSourceActor } = originalLocation;
 
     if (!this.isSourceMapped) {
       if (!this._setBreakpointAtGeneratedLocation(
         actor,
         GeneratedLocation.fromOriginalLocation(originalLocation)
       )) {
-        const scripts = this.scripts.getScriptsBySourceActorAndLine(
-          this,
-          originalLine
-        );
+        const query = { line: originalLine };
+        // For most cases, we have a real source to query for. The
+        // only time we don't is for HTML pages. In that case we want
+        // to query for scripts in an HTML page based on its URL, as
+        // there could be several sources within an HTML page.
+        if (this.source) {
+          query.source = this.source;
+        } else {
+          query.url = this.url;
+        }
+        const scripts = this.dbg.findScripts(query);
 
         // Never do breakpoint sliding for column breakpoints.
         // Additionally, never do breakpoint sliding if no scripts
         // exist on this line.
         //
         // Sliding can go horribly wrong if we always try to find the
         // next line with valid entry points in the entire file.
         // Scripts may be completely GCed and we never knew they
@@ -831,21 +837,25 @@ let SourceActor = ActorClassWithSpec(sou
   _setBreakpointAtGeneratedLocation: function (actor, generatedLocation) {
     let {
       generatedSourceActor,
       generatedLine,
       generatedColumn,
       generatedLastColumn
     } = generatedLocation;
 
-    // Find all scripts that match the given source actor and line number.
-    let scripts = this.scripts.getScriptsBySourceActorAndLine(
-      generatedSourceActor,
-      generatedLine
-    );
+    // Find all scripts that match the given source actor and line
+    // number.
+    const query = { line: generatedLine };
+    if (generatedSourceActor.source) {
+      query.source = generatedSourceActor.source;
+    } else {
+      query.url = generatedSourceActor.url;
+    }
+    let scripts = this.dbg.findScripts(query);
 
     scripts = scripts.filter((script) => !actor.hasScript(script));
 
     // Find all entry points that correspond to the given location.
     let entryPoints = [];
     if (generatedColumn === undefined) {
       // This is a line breakpoint, so we are interested in all offsets
       // that correspond to the given line number.

deleted file mode 100644
--- a/devtools/server/actors/utils/ScriptStore.js
+++ /dev/null
@@ -1,219 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
-/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-const { noop } = require("devtools/shared/DevToolsUtils");
-
-/**
- * A `ScriptStore` is a cache of `Debugger.Script` instances. It holds strong
- * references to the cached scripts to alleviate the GC-sensitivity issues that
- * plague `Debugger.prototype.findScripts`, but this means that its lifetime
- * must be managed carefully. It is the `ScriptStore` user's responsibility to
- * ensure that the `ScriptStore` stays up to date.
- *
- * Implementation Notes:
- *
- * The ScriptStore's prototype methods are very hot, in general. To help the
- * JIT, they avoid ES6-isms and higher-order iteration functions, for the most
- * part. You might be wondering why we don't maintain indices on, say,
- * Debugger.Source for faster querying, if these methods are so hot. First, the
- * hottest method is actually just getting all scripts; second, populating the
- * store becomes prohibitively expensive. So we fall back to linear queries
- * (which isn't so bad, because Debugger.prototype.findScripts is also linear).
- */
-function ScriptStore() {
-  // Set of every Debugger.Script in the cache.
-  this._scripts = new NoDeleteSet;
-}
-
-module.exports = ScriptStore;
-
-ScriptStore.prototype = {
-  // Populating a ScriptStore.
-
-  /**
-   * Add one script to the cache.
-   *
-   * @param Debugger.Script script
-   */
-  addScript(script) {
-    this._scripts.add(script);
-  },
-
-  /**
-   * Add many scripts to the cache at once.
-   *
-   * @param Array scripts
-   *        The set of Debugger.Scripts to add to the cache.
-   */
-  addScripts(scripts) {
-    for (var i = 0, len = scripts.length; i < len; i++) {
-      this.addScript(scripts[i]);
-    }
-  },
-
-  // Querying a ScriptStore.
-
-  /**
-   * Get all the sources for which we have scripts cached.
-   *
-   * @returns Array of Debugger.Source
-   */
-  getSources() {
-    return [...new Set(this._scripts.items.map(s => s.source))];
-  },
-
-  /**
-   * Get all the scripts in the cache.
-   *
-   * @returns read-only Array of Debugger.Script.
-   *
-   * NB: The ScriptStore retains ownership of the returned array, and the
-   * ScriptStore's consumers MUST NOT MODIFY its contents!
-   */
-  getAllScripts() {
-    return this._scripts.items;
-  },
-
-  getScriptsBySourceActor(sourceActor) {
-    return sourceActor.source ?
-           this.getScriptsBySource(sourceActor.source) :
-           this.getScriptsByURL(sourceActor._originalUrl);
-  },
-
-  getScriptsBySourceActorAndLine(sourceActor, line) {
-    return sourceActor.source ?
-           this.getScriptsBySourceAndLine(sourceActor.source, line) :
-           this.getScriptsByURLAndLine(sourceActor._originalUrl, line);
-  },
-
-  /**
-   * Get all scripts produced from the given source.
-   *
-   * @oaram Debugger.Source source
-   * @returns Array of Debugger.Script
-   */
-  getScriptsBySource(source) {
-    var results = [];
-    var scripts = this._scripts.items;
-    var length = scripts.length;
-    for (var i = 0; i < length; i++) {
-      if (scripts[i].source === source) {
-        results.push(scripts[i]);
-      }
-    }
-    return results;
-  },
-
-  /**
-   * Get all scripts produced from the given source whose source code definition
-   * spans the given line.
-   *
-   * @oaram Debugger.Source source
-   * @param Number line
-   * @returns Array of Debugger.Script
-   */
-  getScriptsBySourceAndLine(source, line) {
-    var results = [];
-    var scripts = this._scripts.items;
-    var length = scripts.length;
-    for (var i = 0; i < length; i++) {
-      var script = scripts[i];
-      if (script.source === source &&
-          script.startLine <= line &&
-          (script.startLine + script.lineCount) > line) {
-        results.push(script);
-      }
-    }
-    return results;
-  },
-
-  /**
-   * Get all scripts defined by a source at the given URL.
-   *
-   * @param String url
-   * @returns Array of Debugger.Script
-   */
-  getScriptsByURL(url) {
-    var results = [];
-    var scripts = this._scripts.items;
-    var length = scripts.length;
-    for (var i = 0; i < length; i++) {
-      if (scripts[i].url === url) {
-        results.push(scripts[i]);
-      }
-    }
-    return results;
-  },
-
-  /**
-   * Get all scripts defined by a source a the given URL and whose source code
-   * definition spans the given line.
-   *
-   * @param String url
-   * @param Number line
-   * @returns Array of Debugger.Script
-   */
-  getScriptsByURLAndLine(url, line) {
-    var results = [];
-    var scripts = this._scripts.items;
-    var length = scripts.length;
-    for (var i = 0; i < length; i++) {
-      var script = scripts[i];
-      if (script.url === url &&
-          script.startLine <= line &&
-          (script.startLine + script.lineCount) > line) {
-        results.push(script);
-      }
-    }
-    return results;
-  },
-};
-
-
-/**
- * A set which can only grow, and does not support the delete operation.
- * Provides faster iteration than the native Set by maintaining an array of all
- * items, in addition to the internal set of all items, which allows direct
- * iteration (without the iteration protocol and calling into C++, which are
- * both expensive).
- */
-function NoDeleteSet() {
-  this._set = new Set();
-  this.items = [];
-}
-
-NoDeleteSet.prototype = {
-  /**
-   * An array containing every item in the set for convenience and faster
-   * iteration. This is public for reading only, and consumers MUST NOT modify
-   * this array!
-   */
-  items: null,
-
-  /**
-   * Add an item to the set.
-   *
-   * @param any item
-   */
-  add(item) {
-    if (!this._set.has(item)) {
-      this._set.add(item);
-      this.items.push(item);
-    }
-  },
-
-  /**
-   * Return true if the item is in the set, false otherwise.
-   *
-   * @param any item
-   * @returns Boolean
-   */
-  has(item) {
-    return this._set.has(item);
-  }
-};

--- a/devtools/server/actors/utils/moz.build
+++ b/devtools/server/actors/utils/moz.build
@@ -5,13 +5,12 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 DevToolsModules(
     'actor-registry-utils.js',
     'audionodes.json',
     'automation-timeline.js',
     'make-debugger.js',
     'map-uri-to-addon-id.js',
-    'ScriptStore.js',
     'stack.js',
     'TabSources.js',
     'walker-search.js'
 )

deleted file mode 100644
--- a/devtools/server/tests/unit/test_ScriptStore.js
+++ /dev/null
@@ -1,168 +0,0 @@
-/* -*- js-indent-level: 2; indent-tabs-mode: nil -*- */
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-// Test the functionality of ScriptStore.
-
-const ScriptStore = require("devtools/server/actors/utils/ScriptStore");
-
-// Fixtures
-
-const firstSource = "firstSource";
-const secondSource = "secondSource";
-const thirdSource = "thirdSource";
-
-const scripts = new Set([
-  {
-    url: "a.js",
-    source: firstSource,
-    startLine: 1,
-    lineCount: 100,
-    global: "g1"
-  },
-  {
-    url: "a.js",
-    source: firstSource,
-    startLine: 1,
-    lineCount: 40,
-    global: "g1"
-  },
-  {
-    url: "a.js",
-    source: firstSource,
-    startLine: 50,
-    lineCount: 100,
-    global: "g1"
-  },
-  {
-    url: "a.js",
-    source: firstSource,
-    startLine: 60,
-    lineCount: 90,
-    global: "g1"
-  },
-  {
-    url: "index.html",
-    source: secondSource,
-    startLine: 150,
-    lineCount: 1,
-    global: "g2"
-  },
-  {
-    url: "index.html",
-    source: thirdSource,
-    startLine: 200,
-    lineCount: 100,
-    global: "g2"
-  },
-  {
-    url: "index.html",
-    source: thirdSource,
-    startLine: 250,
-    lineCount: 10,
-    global: "g2"
-  },
-  {
-    url: "index.html",
-    source: thirdSource,
-    startLine: 275,
-    lineCount: 5,
-    global: "g2"
-  }
-]);
-
-function contains(script, line) {
-  return script.startLine <= line &&
-    line < script.startLine + script.lineCount;
-}
-
-function run_test() {
-  testAddScript();
-  testAddScripts();
-  testGetSources();
-  testGetScriptsBySource();
-  testGetScriptsBySourceAndLine();
-  testGetScriptsByURL();
-  testGetScriptsByURLAndLine();
-}
-
-function testAddScript() {
-  const ss = new ScriptStore();
-
-  for (let s of scripts) {
-    ss.addScript(s);
-  }
-
-  equal(ss.getAllScripts().length, scripts.size);
-
-  for (let s of ss.getAllScripts()) {
-    ok(scripts.has(s));
-  }
-}
-
-function testAddScripts() {
-  const ss = new ScriptStore();
-  ss.addScripts([...scripts]);
-
-  equal(ss.getAllScripts().length, scripts.size);
-
-  for (let s of ss.getAllScripts()) {
-    ok(scripts.has(s));
-  }
-}
-
-function testGetSources() {
-  const ss = new ScriptStore();
-  ss.addScripts([...scripts]);
-
-  const expected = new Set([firstSource, secondSource, thirdSource]);
-  const actual = ss.getSources();
-  equal(expected.size, actual.length);
-
-  for (let s of actual) {
-    ok(expected.has(s));
-    expected.delete(s);
-  }
-}
-
-function testGetScriptsBySource() {
-  const ss = new ScriptStore();
-  ss.addScripts([...scripts]);
-
-  const expected = [...scripts].filter(s => s.source === thirdSource);
-  const actual = ss.getScriptsBySource(thirdSource);
-
-  deepEqual(actual, expected);
-}
-
-function testGetScriptsBySourceAndLine() {
-  const ss = new ScriptStore();
-  ss.addScripts([...scripts]);
-
-  const expected = [...scripts].filter(
-    s => s.source === firstSource && contains(s, 65));
-  const actual = ss.getScriptsBySourceAndLine(firstSource, 65);
-
-  deepEqual(actual, expected);
-}
-
-function testGetScriptsByURL() {
-  const ss = new ScriptStore();
-  ss.addScripts([...scripts]);
-
-  const expected = [...scripts].filter(s => s.url === "index.html");
-  const actual = ss.getScriptsByURL("index.html");
-
-  deepEqual(actual, expected);
-}
-
-function testGetScriptsByURLAndLine() {
-  const ss = new ScriptStore();
-  ss.addScripts([...scripts]);
-
-  const expected = [...scripts].filter(
-    s => s.url === "index.html" && contains(s, 250));
-  const actual = ss.getScriptsByURLAndLine("index.html", 250);
-
-  deepEqual(actual, expected);
-}

--- a/devtools/server/tests/unit/xpcshell.ini
+++ b/devtools/server/tests/unit/xpcshell.ini
@@ -32,17 +32,16 @@ support-files =
   setBreakpoint-on-line-with-no-offsets-in-gcd-script.js
   addons/web-extension/manifest.json
   addons/web-extension2/manifest.json
 
 [test_addon_reload.js]
 [test_addons_actor.js]
 [test_animation_name.js]
 [test_animation_type.js]
-[test_ScriptStore.js]
 [test_actor-registry-actor.js]
 [test_nesting-01.js]
 [test_nesting-02.js]
 [test_nesting-03.js]
 [test_forwardingprefix.js]
 [test_getyoungestframe.js]
 [test_nsjsinspector.js]
 [test_dbgactor.js]