Enforce queries' new availability semantics.

third_party/WebKit/Source/modules/webgl/WebGLQuery.h

 // 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.
 
 #ifndef WebGLQuery_h
 #define WebGLQuery_h
 
 #include "modules/webgl/WebGLSharedPlatform3DObject.h"
 
 namespace blink {
 
 class WebGL2RenderingContextBase;
 
-class WebGLQuery : public WebGLSharedPlatform3DObject {
+class WebGLQuery : public WebGLSharedPlatform3DObject, public WebThread::TaskObserver {
     DEFINE_WRAPPERTYPEINFO();
 public:
     ~WebGLQuery() override;
 
     static WebGLQuery* create(WebGL2RenderingContextBase*);
 
     void setTarget(GLenum);
+    bool hasTarget() const { return m_target != 0; }
     GLenum getTarget() const { return m_target; }
 
+    void resetCachedResult();
+    void updateCachedResult(WebGraphicsContext3D*);
+
+    bool isQueryResultAvailable();
+    GLuint getQueryResult();
+
 protected:
     explicit WebGLQuery(WebGL2RenderingContextBase*);
 
     void deleteObjectImpl(WebGraphicsContext3D*) override;
 
 private:
     bool isQuery() const override { return true; }
 
+    void registerTaskObserver();
+    void unregisterTaskObserver();
+
+    // TaskObserver implementation.
+    void didProcessTask() override;
+    void willProcessTask() override { }
+
     GLenum m_target;
+
+    bool m_taskObserverRegistered;
+    bool m_canUpdateAvailability;
+    bool m_queryResultAvailable;
+    GLuint m_queryResult;
 };
 
 } // namespace blink
 
 #endif // WebGLQuery_h