Calculate pixel config and stencil fmt pairs once per pixel config.

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 8a044673919c29b9ebf53279d0b39658c549a941..25dafaf2795dd5287947df3c65a5ecf2a6c08d9c 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -126,6 +126,9 @@ private:
     bool createStencilAttachmentForRenderTarget(GrRenderTarget* rt, int width, int height) override;
     bool attachStencilAttachmentToRenderTarget(GrStencilAttachment* sb,
                                                GrRenderTarget* rt) override;
+    // Given a GrPixelConfig return the index into the stencil format array on GrGLCaps to a
+    // compatible stencil format.
+    int getCompatibleStencilIndex(GrPixelConfig config);
 
     void onClear(GrRenderTarget*, const SkIRect& rect, GrColor color) override;
 
@@ -489,9 +492,9 @@ private:
 
     ///@}
 
-    // we record what stencil format worked last time to hopefully exit early
-    // from our loop that tries stencil formats and calls check fb status.
-    int fLastSuccessfulStencilFmtIdx;
+    // Mapping of pixel configs to know supported stencil formats to be used

[jvanverth1, 2015/09/10 13:35:03]

Nits: know -> known
      adding as -> when adding

[egdaniel, 2015/09/10 13:59:10]

Done.

+    // adding as stencil buffer.
+    int fPixelConfigToStencilIndex[kGrPixelConfigCnt];
 
     typedef GrGpu INHERITED;
     friend class GrGLPathRendering; // For accessing setTextureUnit.