[wrapper-tracing] WebGL and friends: Add write barriers

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
index b41167dffcebd9d3496aece0e5c3baa3def9f761..00a8b3881a6b87df0a05305d39d73f31bab5db3e 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -27,6 +27,7 @@
 
 #include "bindings/core/v8/ExceptionMessages.h"
 #include "bindings/core/v8/ExceptionState.h"
+#include "bindings/core/v8/ScriptWrappableVisitor.h"
 #include "bindings/core/v8/V8BindingMacros.h"
 #include "bindings/modules/v8/HTMLCanvasElementOrOffscreenCanvas.h"
 #include "bindings/modules/v8/WebGLAny.h"
@@ -977,6 +978,11 @@ WebGLRenderingContextBase::WebGLRenderingContextBase(
           &WebGLRenderingContextBase::dispatchContextLostEvent),
       m_restoreAllowed(false),
       m_restoreTimer(this, &WebGLRenderingContextBase::maybeRestoreContext),
+      m_boundArrayBuffer(this, nullptr),
+      m_boundVertexArrayObject(this, nullptr),
+      m_currentProgram(this, nullptr),
+      m_framebufferBinding(this, nullptr),
+      m_renderbufferBinding(this, nullptr),
       m_generatedImageCache(4),
       m_synthesizedErrorsToConsole(true),
       m_numGLErrorsToConsoleAllowed(maxGLErrorsAllowedToConsole),
@@ -1767,6 +1773,7 @@ void WebGLRenderingContextBase::bindTexture(GLenum target,
     synthesizeGLError(GL_INVALID_ENUM, "bindTexture", "invalid target");
     return;
   }
+  ScriptWrappableVisitor::writeBarrier(this, texture);

[Michael Lippautz, 2016/10/12 10:57:12]

TextureUnitState didn't use Member<> types before. I didn't add the
TraceWrapperMembers since I assume having raw pointers is needed for fast
construction/passing around somewhere?

[haraken, 2016/10/12 11:51:28]

How about changing Member<>s in TextureUnitState to TraceWrapperMember<>s? Won't
it work?

[Michael Lippautz, 2016/10/12 12:50:38]

Done.

This exposes one corner case where the compiler doesn't warn us: Pre-sized
containers.

The problem is that when we resize a HeapVector we initialize it with empty
elements. Unlike with ::append (where  the signature makes sure we have the
proper types), it is ok to assign a raw value to m_vector[i] because of the
operator= overload for raw values. Raw assignments (not going through
TraceWrapperMember(this, ...)) to empty TraceWrapperMembers lack the parent
pointer and a DCHECK will fire. 

2 options:
(a) Be fine with that this one case fails at runtime.
(b) Remove the overload for raw values, effectively forcing us to always go
through TraceWrapperMember(..) on aissgnment. 

I'd like to stay with (a).

 
   contextGL()->BindTexture(target, objectOrZero(texture));
   if (texture) {