Specialize base::IsWeakReceiver for Blink weak pointers to support base::Bind (1/5)

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 cdfc165754a0c6ea7129fb5e832593a80cc2646f..56be35281ca5f4dd14b339e92764dde2b08220f6 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -921,7 +921,7 @@ WebGLRenderingContextBase::WebGLRenderingContextBase(HTMLCanvasElement* passedCa
     }
 
     m_drawingBuffer = buffer.release();
-    m_drawingBuffer->addNewMailboxCallback(WTF::bind(&WebGLRenderingContextBase::notifyCanvasContextChanged, createWeakThisPointer()));
+    m_drawingBuffer->addNewMailboxCallback(WTF::bind(&WebGLRenderingContextBase::notifyCanvasContextChanged, wrapWeakPersistent(this)));
     drawingBuffer()->bind(GL_FRAMEBUFFER);
     setupFlags();
 
@@ -1041,13 +1041,13 @@ void WebGLRenderingContextBase::initializeNewContext()
     drawingBuffer()->contextProvider()->setLostContextCallback(
         WebClosure(bind(
             &WebGLRenderingContextBase::forceLostContext,
-            createWeakThisPointer(),
+            wrapWeakPersistent(this),
             WebGLRenderingContextBase::RealLostContext,
             WebGLRenderingContextBase::Auto)));
     drawingBuffer()->contextProvider()->setErrorMessageCallback(
         WebFunction<void(const char*, int32_t)>(bind(
             &WebGLRenderingContextBase::onErrorMessage,
-            createWeakThisPointer())));
+            wrapWeakPersistent(this))));
 
     // If WebGL 2, the PRIMITIVE_RESTART_FIXED_INDEX should be always enabled.
     // See the section <Primitive Restart is Always Enabled> in WebGL 2 spec:
@@ -1158,6 +1158,7 @@ void WebGLRenderingContextBase::destroyContext()
 
     drawingBuffer()->contextProvider()->setLostContextCallback(WebClosure());
     drawingBuffer()->contextProvider()->setErrorMessageCallback(WebFunction<void(const char*, int32_t)>());
+    drawingBuffer()->addNewMailboxCallback(nullptr);

[sof, 2016/06/24 05:24:08]

It makes sense, but why is this needed now?

[tzik, 2016/06/24 05:57:06]

The error caught a Persistent leak after the termination GC.
That's due to DrawingBuffer holds a WeakPersintent of WebGLRendingContextBase
through the WTF::Function, and probably lives after the heap shutdown.
I don't know why the test didn't catch CrossThreadWeakPersistent...

[sof, 2016/06/24 06:45:32]

CT(W)Ps are exempt from checking for leaks when running termination GCs.

But why would the main thread be running a termination GC?

[tzik, 2016/06/24 07:04:58]

Makes sense.
The instance seems to be created on other thread than main according to line
578.

 
     ASSERT(drawingBuffer());
     m_drawingBuffer->beginDestruction();
@@ -6109,7 +6110,7 @@ void WebGLRenderingContextBase::maybeRestoreContext(Timer<WebGLRenderingContextB
     }
 
     m_drawingBuffer = buffer.release();
-    m_drawingBuffer->addNewMailboxCallback(WTF::bind(&WebGLRenderingContextBase::notifyCanvasContextChanged, createWeakThisPointer()));
+    m_drawingBuffer->addNewMailboxCallback(WTF::bind(&WebGLRenderingContextBase::notifyCanvasContextChanged, wrapWeakPersistent(this)));
 
     drawingBuffer()->bind(GL_FRAMEBUFFER);
     m_lostContextErrors.clear();