browser(firefox): support internal drag and drop (#2243)

browser_patches/firefox/BUILD_NUMBER

@@ -1 +1 @@
-1094
+1095

browser_patches/firefox/patches/bootstrap.diff

@@ -3699,10 +3699,10 @@ index 0000000000000000000000000000000000000000..155d0770ddf704728829272a41a31ce8
 +
 diff --git a/juggler/content/PageAgent.js b/juggler/content/PageAgent.js
 new file mode 100644
-index 0000000000000000000000000000000000000000..63754937b3464794227fe894b3d6057fbf0ae582
+index 0000000000000000000000000000000000000000..73b6ee4d266ff648acd0a8dfb8909f9b0c76c28d
 --- /dev/null
 +++ b/juggler/content/PageAgent.js
-@@ -0,0 +1,914 @@
+@@ -0,0 +1,992 @@
 +"use strict";
 +const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");
 +const Ci = Components.interfaces;
@@ -3711,6 +3711,12 @@ index 0000000000000000000000000000000000000000..63754937b3464794227fe894b3d6057f
 +
 +const {Helper} = ChromeUtils.import('chrome://juggler/content/Helper.js');
 +const {NetUtil} = ChromeUtils.import('resource://gre/modules/NetUtil.jsm');
++const dragService = Cc["@mozilla.org/widget/dragservice;1"].getService(
++  Ci.nsIDragService
++);
++const obs = Cc["@mozilla.org/observer-service;1"].getService(
++  Ci.nsIObserverService
++);
 +
 +const helper = new Helper();
 +
@@ -3862,6 +3868,7 @@ index 0000000000000000000000000000000000000000..63754937b3464794227fe894b3d6057f
 +    this._docShell = docShell;
 +    this._initialDPPX = docShell.contentViewer.overrideDPPX;
 +    this._customScrollbars = null;
++    this._dataTransfer = null;
 +  }
 +
 +  async _awaitViewportDimensions({width, height}) {
@@ -4369,6 +4376,12 @@ index 0000000000000000000000000000000000000000..63754937b3464794227fe894b3d6057f
 +  }
 +
 +  async _dispatchKeyEvent({type, keyCode, code, key, repeat, location, text}) {
++    // key events don't fire if we are dragging.
++    if (this._dataTransfer) {
++      if (type === 'keydown' && key === 'Escape')
++        this._cancelDragIfNeeded();
++      return;
++    }
 +    const frame = this._frameTree.mainFrame();
 +    const tip = frame.textInputProcessor();
 +    if (key === 'Meta' && Services.appinfo.OS !== 'Darwin')
@@ -4415,8 +4428,61 @@ index 0000000000000000000000000000000000000000..63754937b3464794227fe894b3d6057f
 +    return {defaultPrevented};
 +  }
 +
++  _startDragSessionIfNeeded() {
++    const sess = dragService.getCurrentSession();
++    if (sess) return;
++    dragService.startDragSessionForTests(
++      Ci.nsIDragService.DRAGDROP_ACTION_MOVE |
++        Ci.nsIDragService.DRAGDROP_ACTION_COPY |
++        Ci.nsIDragService.DRAGDROP_ACTION_LINK
++    );
++  }
++
++  _simulateDragEvent(type, x, y, modifiers) {
++    const window = this._frameTree.mainFrame().domWindow();
++    const element = window.windowUtils.elementFromPoint(x, y, false, false);
++    const event = window.document.createEvent('DragEvent');
++
++    event.initDragEvent(
++      type,
++      true /* bubble */,
++      true /* cancelable */,
++      window,
++      0 /* clickCount */,
++      window.mozInnerScreenX + x,
++      window.mozInnerScreenY + y,
++      x,
++      y,
++      modifiers & 2 /* ctrlkey */,
++      modifiers & 1 /* altKey */,
++      modifiers & 4 /* shiftKey */,
++      modifiers & 8 /* metaKey */,
++      0 /* button */, // firefox always has the button as 0 on drops, regardless of which was pressed
++      null /* relatedTarget */,
++      this._dataTransfer
++    );
++
++    window.windowUtils.dispatchDOMEventViaPresShellForTesting(element, event);
++    if (type === 'drop')
++      dragService.endDragSession(true);
++  }
++
++  _cancelDragIfNeeded() {
++    this._dataTransfer = null;
++    const sess = dragService.getCurrentSession();
++    if (sess)
++      dragService.endDragSession(false);
++  }
++
 +  async _dispatchMouseEvent({type, x, y, button, clickCount, modifiers, buttons}) {
++    this._startDragSessionIfNeeded();
++    const trapDrag = subject => {
++      this._dataTransfer = subject.mozCloneForEvent('drop');
++    }
++
 +    const frame = this._frameTree.mainFrame();
++
++    obs.addObserver(trapDrag, 'on-datatransfer-available');
 +    frame.domWindow().windowUtils.sendMouseEvent(
 +      type,
 +      x,
@@ -4430,6 +4496,8 @@ index 0000000000000000000000000000000000000000..63754937b3464794227fe894b3d6057f
 +      undefined /*isDOMEventSynthesized*/,
 +      undefined /*isWidgetEventSynthesized*/,
 +      buttons);
++    obs.removeObserver(trapDrag, 'on-datatransfer-available');
++
 +    if (type === 'mousedown' && button === 2) {
 +      frame.domWindow().windowUtils.sendMouseEvent(
 +        'contextmenu',
@@ -4445,6 +4513,16 @@ index 0000000000000000000000000000000000000000..63754937b3464794227fe894b3d6057f
 +        undefined /*isWidgetEventSynthesized*/,
 +        buttons);
 +    }
++
++    // update drag state
++    if (this._dataTransfer) {
++      if (type === 'mousemove')
++        this._simulateDragEvent('dragover', x, y, modifiers);
++      else if (type === 'mouseup') // firefox will do drops when any mouse button is released
++        this._simulateDragEvent('drop', x, y, modifiers);
++    } else {
++      this._cancelDragIfNeeded();
++    }
 +  }
 +
 +  async _insertText({text}) {