compositor-worker: Force elements to grow a layer when a CompositorProxy is created.

Source/core/dom/CompositorProxy.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/dom/CompositorProxy.h"
 
 #include "bindings/core/v8/ExceptionMessages.h"
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/dom/DOMNodeIds.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContext.h"
+#include "core/style/ComputedStyle.h"
 
 namespace blink {
 
 struct AttributeFlagMapping {
     const char* name;
     unsigned length;
     CompositorProxy::Attributes attribute;
 };
 
 static AttributeFlagMapping allowedAttributes[] = {
@@ skipping 84 matching lines @@
     return new CompositorProxy(elementId, attributeFlags);
 }
 
 CompositorProxy::CompositorProxy(Element& element, const Vector<String>& attributeArray)
     : m_elementId(DOMNodeIds::idForNode(&element))
     , m_bitfieldsSupported(attributesBitfieldFromNames(attributeArray))
 {
     ASSERT(isMainThread());
     ASSERT(m_bitfieldsSupported);
     ASSERT(sanityCheckAttributeFlags(m_bitfieldsSupported));
+
+    element.setHasCompositorProxy(true);

[Ian Vollick, 2015/04/07 16:40:15]

Where do we set this to false?

[sadrul, 2015/04/07 16:43:23]

We currently do not. The API will need to have a CompositorProxy::disconnect().
If all the CompositorProxy objects for an element (both in the main-thread and
the worker-thread) die, or call disconnect(), then we can safely set this flag
back to false. I am working on that in a separate CL.

+    element.setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::CompositorProxy));
 }
 
 CompositorProxy::CompositorProxy(uint64_t elementId, uint32_t attributeFlags)
     : m_elementId(elementId)
     , m_bitfieldsSupported(attributeFlags)
 {
     ASSERT(isControlThread());
     ASSERT(sanityCheckAttributeFlags(m_bitfieldsSupported));
 }
 
@@ skipping 84 matching lines @@
 
 bool CompositorProxy::raiseExceptionIfNotMutable(Attributes attribute, ExceptionState& exceptionState) const
 {
     if (m_bitfieldsSupported & static_cast<uint32_t>(attribute))
         return false;
     exceptionState.throwDOMException(NoModificationAllowedError, "Attempted to mutate non-mutable attribute.");
     return true;
 }
 
 } // namespace blink