--- a/b2g/chrome/content/shell.js
+++ b/b2g/chrome/content/shell.js
@@ -328,16 +328,17 @@ var shell = {
     window.addEventListener('MozApplicationManifest', this);
     window.addEventListener('mozfullscreenchange', this);
     window.addEventListener('MozAfterPaint', this);
     window.addEventListener('sizemodechange', this);
     window.addEventListener('unload', this);
     this.contentBrowser.addEventListener('mozbrowserloadstart', this, true);
     this.contentBrowser.addEventListener('mozbrowserselectionchange', this, true);
     this.contentBrowser.addEventListener('mozbrowserscrollviewchange', this, true);
+    this.contentBrowser.addEventListener('mozbrowsertouchcarettap', this, true);
 
     CustomEventManager.init();
     WebappsHelper.init();
     UserAgentOverrides.init();
     IndexedDBPromptHelper.init();
     CaptivePortalLoginHelper.init();
 
     this.contentBrowser.src = homeURL;
@@ -356,16 +357,17 @@ var shell = {
     window.removeEventListener('keypress', this, true);
     window.removeEventListener('keyup', this, true);
     window.removeEventListener('MozApplicationManifest', this);
     window.removeEventListener('mozfullscreenchange', this);
     window.removeEventListener('sizemodechange', this);
     this.contentBrowser.removeEventListener('mozbrowserloadstart', this, true);
     this.contentBrowser.removeEventListener('mozbrowserselectionchange', this, true);
     this.contentBrowser.removeEventListener('mozbrowserscrollviewchange', this, true);
+    this.contentBrowser.removeEventListener('mozbrowsertouchcarettap', this, true);
     ppmm.removeMessageListener("content-handler", this);
 
     UserAgentOverrides.uninit();
     IndexedDBPromptHelper.uninit();
   },
 
   // If this key event actually represents a hardware button, filter it here
   // and send a mozChromeEvent with detail.type set to xxx-button-press or
@@ -503,16 +505,22 @@ var shell = {
         this.notifyContentStart();
        break;
       case 'mozbrowserscrollviewchange':
         this.sendChromeEvent({
           type: 'scrollviewchange',
           detail: evt.detail,
         });
         break;
+      case 'mozbrowsertouchcarettap':
+        this.sendChromeEvent({
+          type: 'touchcarettap',
+          detail: evt.detail,
+        });
+        break;
       case 'mozbrowserselectionchange':
         // The mozbrowserselectionchange event, may have crossed the chrome-content boundary.
         // This event always dispatch to shell.js. But the offset we got from this event is
         // based on tab's coordinate. So get the actual offsets between shell and evt.target.
         let elt = evt.target;
         let win = elt.ownerDocument.defaultView;
         let offsetX = win.mozInnerScreenX - window.mozInnerScreenX;
         let offsetY = win.mozInnerScreenY - window.mozInnerScreenY;

--- a/dom/browser-element/BrowserElementChildPreload.js
+++ b/dom/browser-element/BrowserElementChildPreload.js
@@ -221,16 +221,22 @@ BrowserElementChild.prototype = {
                      /* useCapture = */ false,
                      /* wantsUntrusted = */ false);
 
     addEventListener('scrollviewchange',
                      this._ScrollViewChangeHandler.bind(this),
                      /* useCapture = */ false,
                      /* wantsUntrusted = */ false);
 
+    addEventListener('touchcarettap',
+                     this._touchCaretTapHandler.bind(this),
+                     /* useCapture = */ false,
+                     /* wantsUntrusted = */ false);
+
+
     // This listens to unload events from our message manager, but /not/ from
     // the |content| window.  That's because the window's unload event doesn't
     // bubble, and we're not using a capturing listener.  If we'd used
     // useCapture == true, we /would/ hear unload events from the window, which
     // is not what we want!
     addEventListener('unload',
                      this._unloadHandler.bind(this),
                      /* useCapture = */ false,
@@ -626,16 +632,21 @@ BrowserElementChild.prototype = {
 
     if (lang) {
       meta.lang = lang;
     }
 
     sendAsyncMsg('metachange', meta);
   },
 
+  _touchCaretTapHandler: function(e) {
+    e.stopPropagation();
+    sendAsyncMsg('touchcarettap');
+  },
+
   _ScrollViewChangeHandler: function(e) {
     e.stopPropagation();
     let detail = {
       state: e.state,
       scrollX: e.scrollX,
       scrollY: e.scrollY,
     };
     sendAsyncMsg('scrollviewchange', detail);

--- a/dom/browser-element/BrowserElementParent.jsm
+++ b/dom/browser-element/BrowserElementParent.jsm
@@ -253,17 +253,18 @@ BrowserElementParent.prototype = {
       "got-can-go-forward": this._gotDOMRequestResult,
       "fullscreen-origin-change": this._remoteFullscreenOriginChange,
       "rollback-fullscreen": this._remoteFrameFullscreenReverted,
       "exit-fullscreen": this._exitFullscreen,
       "got-visible": this._gotDOMRequestResult,
       "visibilitychange": this._childVisibilityChange,
       "got-set-input-method-active": this._gotDOMRequestResult,
       "selectionchange": this._handleSelectionChange,
-      "scrollviewchange": this._handleScrollViewChange
+      "scrollviewchange": this._handleScrollViewChange,
+      "touchcarettap": this._handleTouchCaretTap
     };
 
     let mmSecuritySensitiveCalls = {
       "showmodalprompt": this._handleShowModalPrompt,
       "contextmenu": this._fireCtxMenuEvent,
       "securitychange": this._fireEventFromMsg,
       "locationchange": this._fireEventFromMsg,
       "iconchange": this._fireEventFromMsg,
@@ -500,16 +501,22 @@ BrowserElementParent.prototype = {
   },
 
   _handleScrollViewChange: function(data) {
     let evt = this._createEvent("scrollviewchange", data.json,
                                 /* cancelable = */ false);
     this._frameElement.dispatchEvent(evt);
   },
 
+  _handleTouchCaretTap: function(data) {
+    let evt = this._createEvent("touchcarettap", data.json,
+                                /* cancelable = */ false);
+    this._frameElement.dispatchEvent(evt);
+  },
+
   _createEvent: function(evtName, detail, cancelable) {
     // This will have to change if we ever want to send a CustomEvent with null
     // detail.  For now, it's OK.
     if (detail !== undefined && detail !== null) {
       detail = Cu.cloneInto(detail, this._window);
       return new this._window.CustomEvent('mozbrowser' + evtName,
                                           { bubbles: true,
                                             cancelable: cancelable,

--- a/layout/base/TouchCaret.cpp
+++ b/layout/base/TouchCaret.cpp
@@ -25,16 +25,17 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/BasicEvents.h"
 #include "nsIDOMWindow.h"
 #include "nsQueryContentEventResult.h"
 #include "nsIInterfaceRequestorUtils.h"
 #include "nsView.h"
 #include "nsDOMTokenList.h"
 #include "nsCaret.h"
+#include "mozilla/dom/CustomEvent.h"
 
 using namespace mozilla;
 
 // To enable all the TOUCHCARET_LOG print statements, change the 0 to 1 in the
 // following #define.
 #define ENABLE_TOUCHCARET_LOG 0
 
 #if ENABLE_TOUCHCARET_LOG
@@ -53,17 +54,18 @@ NS_IMPL_ISUPPORTS(TouchCaret, nsISelecti
 
 /*static*/ int32_t TouchCaret::sTouchCaretInflateSize = 0;
 /*static*/ int32_t TouchCaret::sTouchCaretExpirationTime = 0;
 
 TouchCaret::TouchCaret(nsIPresShell* aPresShell)
   : mState(TOUCHCARET_NONE),
     mActiveTouchId(-1),
     mCaretCenterToDownPointOffsetY(0),
-    mVisible(false)
+    mVisible(false),
+    mIsValidTap(false)
 {
   TOUCHCARET_LOG("Constructor, PresShell=%p", aPresShell);
   MOZ_ASSERT(NS_IsMainThread());
 
   static bool addedTouchCaretPref = false;
   if (!addedTouchCaretPref) {
     Preferences::AddIntVarCache(&sTouchCaretInflateSize,
                                 "touchcaret.inflatesize.threshold");
@@ -596,16 +598,17 @@ TouchCaret::HandleMouseMoveEvent(WidgetM
     case TOUCHCARET_MOUSEDRAG_ACTIVE:
       {
         nsPoint movePoint = GetEventPosition(aEvent);
         movePoint.y += mCaretCenterToDownPointOffsetY;
         nsRect contentBoundary = GetContentBoundary();
         movePoint = contentBoundary.ClampPoint(movePoint);
 
         MoveCaret(movePoint);
+        mIsValidTap = false;
         status = nsEventStatus_eConsumeNoDefault;
       }
       break;
 
     case TOUCHCARET_TOUCHDRAG_ACTIVE:
     case TOUCHCARET_TOUCHDRAG_INACTIVE:
       // Consume mouse event in touch sequence.
       status = nsEventStatus_eConsumeNoDefault;
@@ -633,16 +636,17 @@ TouchCaret::HandleTouchMoveEvent(WidgetT
     case TOUCHCARET_TOUCHDRAG_ACTIVE:
       {
         nsPoint movePoint = GetEventPosition(aEvent, mActiveTouchId);
         movePoint.y += mCaretCenterToDownPointOffsetY;
         nsRect contentBoundary = GetContentBoundary();
         movePoint = contentBoundary.ClampPoint(movePoint);
 
         MoveCaret(movePoint);
+        mIsValidTap = false;
         status = nsEventStatus_eConsumeNoDefault;
       }
       break;
 
     case TOUCHCARET_TOUCHDRAG_INACTIVE:
       // Consume NS_TOUCH_MOVE event in TOUCHCARET_TOUCHDRAG_INACTIVE state.
       status = nsEventStatus_eConsumeNoDefault;
       break;
@@ -844,16 +848,45 @@ TouchCaret::HandleTouchDownEvent(WidgetT
       mTouchesId.AppendElement(aEvent->touches[i]->mIdentifier);
     }
   }
 
   return status;
 }
 
 void
+TouchCaret::DispatchTapEvent()
+{
+  nsCOMPtr<nsIPresShell> presShell = do_QueryReferent(mPresShell);
+  if (!presShell) {
+    return;
+  }
+
+  nsCOMPtr<nsIDocument> doc = presShell->GetDocument();
+  if (!doc) {
+    return;
+  }
+
+  ErrorResult res;
+  nsRefPtr<Event> domEvent =
+    doc->CreateEvent(NS_LITERAL_STRING("CustomEvent"), res);
+  if (res.Failed()) {
+    return;
+  }
+
+  CustomEvent* customEvent = static_cast<CustomEvent*>(domEvent.get());
+  customEvent->InitCustomEvent(NS_LITERAL_STRING("touchcarettap"),
+                               true, false, nullptr);
+  customEvent->SetTrusted(true);
+  customEvent->GetInternalNSEvent()->mFlags.mOnlyChromeDispatch = true;
+  bool ret;
+  doc->DispatchEvent(domEvent, &ret);
+}
+
+void
 TouchCaret::SetState(TouchCaretState aState)
 {
   TOUCHCARET_LOG("state changed from %d to %d", mState, aState);
   if (mState == TOUCHCARET_NONE) {
     MOZ_ASSERT(aState != TOUCHCARET_TOUCHDRAG_INACTIVE,
                "mState: NONE => TOUCHDRAG_INACTIVE isn't allowed!");
   }
 
@@ -874,10 +907,17 @@ TouchCaret::SetState(TouchCaretState aSt
                "TOUCHDRAG_INACTIVE allowed next state: NONE!");
   }
 
   mState = aState;
 
   if (mState == TOUCHCARET_NONE) {
     mActiveTouchId = -1;
     mCaretCenterToDownPointOffsetY = 0;
+    if (mIsValidTap) {
+      DispatchTapEvent();
+      mIsValidTap = false;
+    }
+  } else if (mState == TOUCHCARET_TOUCHDRAG_ACTIVE ||
+             mState == TOUCHCARET_MOUSEDRAG_ACTIVE) {
+    mIsValidTap = true;
   }
 }

--- a/layout/base/TouchCaret.h
+++ b/layout/base/TouchCaret.h
@@ -205,16 +205,21 @@ private:
   };
 
   /**
    * Do actual state transition and reset substates.
    */
   void SetState(TouchCaretState aState);
 
   /**
+   * Dispatch touch caret tap event to chrome.
+   */
+  void DispatchTapEvent();
+
+  /**
    * Current state we're dealing with.
    */
   TouchCaretState mState;
 
   /**
    * Array containing all active touch IDs. When a touch happens, it gets added
    * to this array, even if we choose not to handle it. When it ends, we remove
    * it. We need to maintain this array in order to detect the end of the
@@ -244,16 +249,18 @@ private:
   {
     return sTouchCaretExpirationTime;
   }
 
   nsWeakPtr mPresShell;
 
   // Touch caret visibility
   bool mVisible;
+  // Use for detecting single tap on touch caret.
+  bool mIsValidTap;
   // Touch caret timer
   nsCOMPtr<nsITimer> mTouchCaretExpirationTimer;
 
   // Preference
   static int32_t sTouchCaretInflateSize;
   static int32_t sTouchCaretExpirationTime;
 
   // The auto scroll timer's interval in miliseconds.