cc: Don't discard framebuffer when using partial swaps

cc/output/gl_renderer.h

 // Copyright 2010 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 CC_OUTPUT_GL_RENDERER_H_
 #define CC_OUTPUT_GL_RENDERER_H_
 
 #include "base/cancelable_callback.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/scoped_ptr_vector.h"
@@ skipping 99 matching lines @@
   bool stencil_enabled() const { return stencil_shadow_; }
   void SetBlendEnabled(bool enabled);
   bool blend_enabled() const { return blend_shadow_; }
 
   virtual void BindFramebufferToOutputSurface(DrawingFrame* frame) OVERRIDE;
   virtual bool BindFramebufferToTexture(DrawingFrame* frame,
                                         const ScopedResource* resource,
                                         gfx::Rect target_rect) OVERRIDE;
   virtual void SetDrawViewport(gfx::Rect window_space_viewport) OVERRIDE;
   virtual void SetScissorTestRect(gfx::Rect scissor_rect) OVERRIDE;
-  virtual void ClearFramebuffer(DrawingFrame* frame) OVERRIDE;
+  virtual void DiscardPixels(bool has_external_stencil_test,
+                             bool draw_rect_covers_full_surface) OVERRIDE;
+  virtual void ClearFramebuffer(DrawingFrame* frame,
+                                bool has_external_stencil_test) OVERRIDE;
   virtual void DoDrawQuad(DrawingFrame* frame, const class DrawQuad*) OVERRIDE;
   virtual void BeginDrawingFrame(DrawingFrame* frame) OVERRIDE;
   virtual void FinishDrawingFrame(DrawingFrame* frame) OVERRIDE;
   virtual bool FlippedFramebuffer() const OVERRIDE;
   virtual void EnsureScissorTestEnabled() OVERRIDE;
   virtual void EnsureScissorTestDisabled() OVERRIDE;
   virtual void CopyCurrentRenderPassToBitmap(
       DrawingFrame* frame,
       scoped_ptr<CopyOutputRequest> request) OVERRIDE;
   virtual void FinishDrawingQuadList() OVERRIDE;
@@ skipping 335 matching lines @@
 #if DEBUG_GL_CALLS && !defined(NDEBUG)
 #define GLC(context, x)                                                        \
   (x, GLRenderer::DebugGLCall(&* context, #x, __FILE__, __LINE__))
 #else
 #define GLC(context, x) (x)
 #endif
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_GL_RENDERER_H_