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

src/gpu/gl/GrGLGpu.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLGpu_DEFINED
 #define GrGLGpu_DEFINED
 
@@ skipping 108 matching lines @@
                                          GrGpuResource::LifeCycle lifeCycle,
                                          const void* srcData) override;
     GrVertexBuffer* onCreateVertexBuffer(size_t size, bool dynamic) override;
     GrIndexBuffer* onCreateIndexBuffer(size_t size, bool dynamic) override;
     GrTexture* onWrapBackendTexture(const GrBackendTextureDesc&, GrWrapOwnership) override;
     GrRenderTarget* onWrapBackendRenderTarget(const GrBackendRenderTargetDesc&,
                                               GrWrapOwnership) override;
     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;
 
     void onClearStencilClip(GrRenderTarget*, const SkIRect& rect, bool insideClip) override;
 
     bool onReadPixels(GrSurface*,
                       int left, int top,
                       int width, int height,
                       GrPixelConfig,
                       void* buffer,
@@ skipping 343 matching lines @@
 
     GrPipelineBuilder::DrawFace fHWDrawFace;
     TriState                    fHWWriteToColor;
     TriState                    fHWDitherEnabled;
     uint32_t                    fHWBoundRenderTargetUniqueID;
     TriState                    fHWSRGBFramebuffer;
     SkTArray<uint32_t, true>    fHWBoundTextureUniqueIDs;
 
     ///@}
 
-    // 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 known supported stencil formats to be used
+    // when adding a stencil buffer to a framebuffer.
+    int fPixelConfigToStencilIndex[kGrPixelConfigCnt];
 
     typedef GrGpu INHERITED;
     friend class GrGLPathRendering; // For accessing setTextureUnit.
 };
 
 #endif