[DevTools] Implement dock to left.

third_party/WebKit/Source/devtools/front_end/ui/SoftContextMenu.js

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 64 matching lines @@
       this._glassPaneElement.addEventListener('mouseup', this._glassPaneMouseUp.bind(this), false);
       this._glassPaneElement.appendChild(this.element);
       document.body.appendChild(this._glassPaneElement);
       this._discardMenuOnResizeListener = this._discardMenu.bind(this, true);
       document.defaultView.addEventListener('resize', this._discardMenuOnResizeListener, false);
     } else {
       this._parentMenu._parentGlassPaneElement().appendChild(this.element);
     }
 
     // Re-position menu in case it does not fit.
-    if (document.body.offsetWidth < this.element.offsetLeft + this.element.offsetWidth) {
-      this.element.style.left =
-          Math.max(
-              UI.Dialog.modalHostView().element.totalOffsetLeft(), this._parentMenu ?
-                  this._parentMenu.element.offsetLeft - this.element.offsetWidth + subMenuOverlap :
-                  document.body.offsetWidth - this.element.offsetWidth) +
-          'px';
+    var hostLeft = UI.Dialog.modalHostView().element.totalOffsetLeft();
+    var hostRight = hostLeft + UI.Dialog.modalHostView().element.offsetWidth;
+    if (hostRight < this.element.offsetLeft + this.element.offsetWidth) {
+      var left = this._parentMenu ? this._parentMenu.element.offsetLeft - this.element.offsetWidth + subMenuOverlap :
+                                    hostRight - this.element.offsetWidth;
+      this.element.style.left = Math.max(hostLeft, left) + 'px';
     }
 
     // Move submenus upwards if it does not fit.
     if (this._parentMenu && document.body.offsetHeight < this.element.offsetTop + this.element.offsetHeight) {
       y = Math.max(
           UI.Dialog.modalHostView().element.totalOffsetTop(), document.body.offsetHeight - this.element.offsetHeight);
       this.element.style.top = y + 'px';
     }
 
     var maxHeight = UI.Dialog.modalHostView().element.offsetHeight;
@@ skipping 283 matching lines @@
 
   _discardSubMenus() {
     if (this._subMenu)
       this._subMenu._discardSubMenus();
     if (this.element)
       this.element.remove();
     if (this._parentMenu)
       delete this._parentMenu._subMenu;
   }
 };