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..fe112b8bacbdf18dc5b26406d21455909c7815d9 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 onInsertEventMarker(const char* marker) SK_OVERRIDE;
+    virtual void onPushGroupMarker(const char* marker) SK_OVERRIDE;
+    virtual void onPopGroupMarker() SK_OVERRIDE;
+
     virtual void onGpuDraw(const DrawInfo&) SK_OVERRIDE;
 
     virtual void onGpuStencilPath(const GrPath*, SkPath::FillType) SK_OVERRIDE;