Add hooks for GL_EXT_debug_marker in gpu

src/gpu/gl/GrGpuGL.h

Index: src/gpu/gl/GrGpuGL.h
diff --git a/src/gpu/gl/GrGpuGL.h b/src/gpu/gl/GrGpuGL.h
index edd58c44bc8675290873d6942d5bd30ac0699339..cc115465f4186904f953c2d95333a095cc5e4569 100644
--- a/src/gpu/gl/GrGpuGL.h
+++ b/src/gpu/gl/GrGpuGL.h
@@ -152,6 +152,10 @@ private:
 
     virtual void onResolveRenderTarget(GrRenderTarget* target) SK_OVERRIDE;
 
+    virtual void onInstantGpuTraceEvent(const char* marker) SK_OVERRIDE;
+    virtual void onPushGpuTraceEvent(const char* marker) SK_OVERRIDE;
+    virtual void onPopGpuTraceEvent() SK_OVERRIDE;
+
     virtual void onGpuDraw(const DrawInfo&) SK_OVERRIDE;
 
     virtual void onGpuStencilPath(const GrPath*, SkPath::FillType) SK_OVERRIDE;