--- a/devtools/client/commandline/test/browser_gcli_telemetry.js
+++ b/devtools/client/commandline/test/browser_gcli_telemetry.js
@@ -74,49 +74,52 @@ function* spawnTest() {
  * it.
  * Store all recordings in Telemetry.telemetryInfo.
  * @return {Telemetry}
  */
 function loadTelemetryAndRecordLogs() {
   info("Mock the Telemetry log function to record logged information");
 
   let Telemetry = require("devtools/client/shared/telemetry");
-
   Telemetry.prototype.telemetryInfo = {};
   Telemetry.prototype._oldlog = Telemetry.prototype.log;
   Telemetry.prototype.log = function (histogramId, value) {
     if (!this.telemetryInfo) {
       // Telemetry instance still in use after stopRecordingTelemetryLogs
       return;
     }
     if (histogramId) {
       if (!this.telemetryInfo[histogramId]) {
         this.telemetryInfo[histogramId] = [];
       }
       this.telemetryInfo[histogramId].push(value);
     }
   };
+  Telemetry.prototype._oldlogScalar = Telemetry.prototype.logScalar;
+  Telemetry.prototype.logScalar = Telemetry.prototype.log;
   Telemetry.prototype._oldlogKeyed = Telemetry.prototype.logKeyed;
   Telemetry.prototype.logKeyed = function (histogramId, key, value) {
     this.log(`${histogramId}|${key}`, value);
   };
 
   return Telemetry;
 }
 
 /**
  * Stop recording the Telemetry logs and put back the utils as it was before.
  * @param {Telemetry} Required Telemetry
  *        Telemetry object that needs to be stopped.
  */
 function stopRecordingTelemetryLogs(Telemetry) {
   info("Stopping Telemetry");
   Telemetry.prototype.log = Telemetry.prototype._oldlog;
+  Telemetry.prototype.logScalar = Telemetry.prototype._oldlogScalar;
   Telemetry.prototype.logKeyed = Telemetry.prototype._oldlogKeyed;
   delete Telemetry.prototype._oldlog;
+  delete Telemetry.prototype._oldlogScalar;
   delete Telemetry.prototype._oldlogKeyed;
   delete Telemetry.prototype.telemetryInfo;
 }
 
 function checkTelemetryResults(results) {
   let prefix = COMMAND_HISTOGRAM_ID + "|";
   let keys = Object.keys(results).filter(result => {
     return result.startsWith(prefix);

--- a/devtools/client/framework/test/shared-head.js
+++ b/devtools/client/framework/test/shared-head.js
@@ -579,34 +579,38 @@ function loadTelemetryAndRecordLogs() {
     }
     if (histogramId) {
       if (!this.telemetryInfo[histogramId]) {
         this.telemetryInfo[histogramId] = [];
       }
       this.telemetryInfo[histogramId].push(value);
     }
   };
+  Telemetry.prototype._oldlogScalar = Telemetry.prototype.logScalar;
+  Telemetry.prototype.logScalar = Telemetry.prototype.log;
   Telemetry.prototype._oldlogKeyed = Telemetry.prototype.logKeyed;
   Telemetry.prototype.logKeyed = function (histogramId, key, value) {
     this.log(`${histogramId}|${key}`, value);
   };
 
   return Telemetry;
 }
 
 /**
  * Stop recording the Telemetry logs and put back the utils as it was before.
  * @param {Telemetry} Required Telemetry
  *        Telemetry object that needs to be stopped.
  */
 function stopRecordingTelemetryLogs(Telemetry) {
   info("Stopping Telemetry");
   Telemetry.prototype.log = Telemetry.prototype._oldlog;
+  Telemetry.prototype.logScalar = Telemetry.prototype._oldlogScalar;
   Telemetry.prototype.logKeyed = Telemetry.prototype._oldlogKeyed;
   delete Telemetry.prototype._oldlog;
+  delete Telemetry.prototype._oldlogScalar;
   delete Telemetry.prototype._oldlogKeyed;
   delete Telemetry.prototype.telemetryInfo;
 }
 
 /**
  * Clean the logical clipboard content. This method only clears the OS clipboard on
  * Windows (see Bug 666254).
  */

--- a/devtools/client/shared/telemetry.js
+++ b/devtools/client/shared/telemetry.js
@@ -194,16 +194,19 @@ Telemetry.prototype = {
     let charts = this._histograms[id] || this._histograms.custom;
 
     if (charts.histogram) {
       this.log(charts.histogram, true);
     }
     if (charts.timerHistogram) {
       this.startTimer(charts.timerHistogram);
     }
+    if (charts.scalar) {
+      this.logScalar(charts.scalar, 1);
+    }
   },
 
   /**
    * Record that an action occurred.  Aliases to `toolOpened`, so it's just for
    * readability at the call site for cases where we aren't actually opening
    * tools.
    */
   actionOccurred(id) {
@@ -255,24 +258,54 @@ Telemetry.prototype = {
    * Log a value to a histogram.
    *
    * @param  {String} histogramId
    *         Histogram in which the data is to be stored.
    * @param  value
    *         Value to store.
    */
   log: function (histogramId, value) {
-    if (histogramId) {
-      try {
-        let histogram = Services.telemetry.getHistogramById(histogramId);
-        histogram.add(value);
-      } catch (e) {
-        dump("Warning: An attempt was made to write to the " + histogramId +
-             " histogram, which is not defined in Histograms.json\n");
+    if (!histogramId) {
+      return;
+    }
+
+    try {
+      let histogram = Services.telemetry.getHistogramById(histogramId);
+      histogram.add(value);
+    } catch (e) {
+      dump(`Warning: An attempt was made to write to the ${histogramId} ` +
+           `histogram, which is not defined in Histograms.json\n`);
+    }
+  },
+
+  /**
+   * Log a value to a scalar.
+   *
+   * @param  {String} scalarId
+   *         Scalar in which the data is to be stored.
+   * @param  value
+   *         Value to store.
+   */
+  logScalar: function (scalarId, value) {
+    if (!scalarId) {
+      return;
+    }
+
+    try {
+      if (isNaN(value)) {
+        dump(`Warning: An attempt was made to write a non-numeric value ` +
+             `${value} to the ${scalarId} scalar. Only numeric values are ` +
+             `allowed.`);
+
+        return;
       }
+      Services.telemetry.scalarSet(scalarId, value);
+    } catch (e) {
+      dump(`Warning: An attempt was made to write to the ${scalarId} ` +
+           `scalar, which is not defined in Scalars.yaml\n`);
     }
   },
 
   /**
    * Log a value to a keyed histogram.
    *
    * @param  {String} histogramId
    *         Histogram in which the data is to be stored.
@@ -287,18 +320,18 @@ Telemetry.prototype = {
         let histogram = Services.telemetry.getKeyedHistogramById(histogramId);
 
         if (typeof value === "undefined") {
           histogram.add(key);
         } else {
           histogram.add(key, value);
         }
       } catch (e) {
-        dump("Warning: An attempt was made to write to the " + histogramId +
-             " histogram, which is not defined in Histograms.json\n");
+        dump(`Warning: An attempt was made to write to the ${histogramId} ` +
+             `histogram, which is not defined in Histograms.json\n`);
       }
     }
   },
 
   /**
    * Log info about usage once per browser version. This allows us to discover
    * how many individual users are using our tools for each browser version.
    *