Implement HTMLMarqueeElement's animation in private scripts

Source/core/html/HTMLMarqueeElement.js

Index: Source/core/html/HTMLMarqueeElement.js
diff --git a/Source/core/html/HTMLMarqueeElement.js b/Source/core/html/HTMLMarqueeElement.js
index b18756327e29177580caa63a03ee0f0a09b72ccc..b0e00a1d0d27095d74928356f0c5758112c094fb 100644
--- a/Source/core/html/HTMLMarqueeElement.js
+++ b/Source/core/html/HTMLMarqueeElement.js
@@ -81,32 +81,6 @@ installClass('HTMLMarqueeElement', function(global) {
         });
     }
 
-    function defineInlineEventHandler(prototype, eventName) {
-        var propertyName = 'on' + eventName;
-        // FIXME: We should use symbols here instead.
-        var functionPropertyName = propertyName + 'Function_';
-        var eventHandlerPropertyName = propertyName + 'EventHandler_';
-        Object.defineProperty(prototype, propertyName, {
-            get: function() {
-                var func = this[functionPropertyName];
-                return func || null;
-            },
-            set: function(value) {
-                var oldEventHandler = this[eventHandlerPropertyName];
-                if (oldEventHandler)
-                    this.removeEventListener(eventName, oldEventHandler);
-                // Notice that we wrap |value| in an anonymous function so that the
-                // author can't call removeEventListener themselves to unregister the
-                // inline event handler.
-                var newEventHandler = value ? function() { value.apply(this, arguments) } : null;
-                if (newEventHandler)
-                    this.addEventListener(eventName, newEventHandler);
-                this[functionPropertyName] = value;
-                this[eventHandlerPropertyName] = newEventHandler;
-            },
-        });
-    }
-
     var HTMLMarqueeElementPrototype = Object.create(HTMLElement.prototype);
 
     reflectAttribute(HTMLMarqueeElementPrototype, 'behavior', 'behavior');
@@ -118,10 +92,6 @@ installClass('HTMLMarqueeElement', function(global) {
     reflectAttribute(HTMLMarqueeElementPrototype, 'width', 'width');
     reflectBooleanAttribute(HTMLMarqueeElementPrototype, 'truespeed', 'trueSpeed');
 
-    defineInlineEventHandler(HTMLMarqueeElementPrototype, 'start');
-    defineInlineEventHandler(HTMLMarqueeElementPrototype, 'finish');
-    defineInlineEventHandler(HTMLMarqueeElementPrototype, 'bounce');

[haraken, 2014/07/15 12:57:07]

I removed these event handlers, since we haven't yet supported these event
handlers in Blink.

-
     HTMLMarqueeElementPrototype.createdCallback = function() {

[haraken, 2014/07/15 12:57:07]

abarth@: When and how are you assuming that these callbacks are called back? In
my understanding:

- createCallback should be called from C++ when the marquee element is created.

- detachedCallback should be called from C++ when ActiveDOMObject is suspended.

- attachedCallback should be called from C++ when ActiveDOMObject is resumed.

- attributeChangedCallback should be called from C++ when
RenderMarquee::styleDidChange is called.

- We'll be able to get rid of almost all implementations from
HTMLMarqueeElement.cpp and RenderMarquee.cpp, but a couple of code will stay
there to invoke those callbacks in private scripts.

Am I understanding correctly?

[abarth-chromium, 2014/07/15 17:10:07]

These callbacks are all defined by
http://w3c.github.io/webcomponents/spec/custom/.  You shouldn't have to write
any code to trigger these callbacks.  All the machinery should already exist. 
Take a look at V8CustomElementLifecycleCallbacks, which knows how to call the
callbacks.  If you run the <i-marquee> script in a normal page, you can set some
breakpoints in V8CustomElementLifecycleCallbacks to see how the callbacks get
called.

The machinery for calling these callbacks seems to already understand isolated
worlds.  We just need to create them in the proper v8::Context, presumably
around the time the HTMLMarqueeElement is created by the HTMLElementFactory.
We'll be able to delete RenderMarquee entirely.  I think we can delete almost
all of HTMLMarqueeElement.  We'll need to keep just enough to register the
custom script version as a custom element.

         var shadow = this.createShadowRoot();
         var style = global.document.createElement('style');
@@ -364,7 +334,6 @@ installClass('HTMLMarqueeElement', function(global) {
     HTMLMarqueeElementPrototype.continue_ = function() {
         if (!this.shouldContinue_()) {
             this.player_ = null;
-            this.dispatchEvent(new Event('finish', false, true));
             return;
         }
 
@@ -385,8 +354,6 @@ installClass('HTMLMarqueeElement', function(global) {
                 return;
             ++this.loopCount_;
             this.continue_();
-            if (this.player_ && this.behavior === kBehaviorAlternate)
-                this.dispatchEvent(new Event('bounce', false, true));
         }.bind(this));
     };
 
@@ -397,7 +364,6 @@ installClass('HTMLMarqueeElement', function(global) {
             this.continueCallback_ = null;
             this.continue_();
         }.bind(this));
-        this.dispatchEvent(new Event('start', false, true));
     };
 
     HTMLMarqueeElementPrototype.stop = function() {