Initial refactoring to enable the addition of the SkiaOpenGLPipeline.

Test: existing and new HWUI unit tests all pass.
Change-Id: I4f5c1dc839a2ed15d8b0f6245fe030684501b083
diff --git a/libs/hwui/renderthread/IRenderPipeline.h b/libs/hwui/renderthread/IRenderPipeline.h
index 97cdf7f..f96c2fd 100644
--- a/libs/hwui/renderthread/IRenderPipeline.h
+++ b/libs/hwui/renderthread/IRenderPipeline.h
@@ -22,6 +22,8 @@
 #include <SkRect.h>
 #include <utils/RefBase.h>
 
+class GrContext;
+
 namespace android {
 
 class Surface;
@@ -43,6 +45,8 @@
     Succeeded
 };
 
+class Frame;
+
 class IRenderPipeline {
 public:
     virtual MakeCurrentResult makeCurrent() = 0;
@@ -69,6 +73,7 @@
     virtual TaskManager* getTaskManager() = 0;
     virtual bool createOrUpdateLayer(RenderNode* node,
             const DamageAccumulator& damageAccumulator) = 0;
+    virtual GrContext* getGrContext() = 0;
 
     virtual ~IRenderPipeline() {}
 };