Add a makeDrawContextWithFallback that handles config fallback

include/gpu/GrContext.h

Index: include/gpu/GrContext.h
diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index 5785553dfdeae753b36233d1c81b2e3bfa663cea..f14c36e35cab1c2443084ea9cde86859a02f4dc9 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -194,6 +194,22 @@ public:
                                          const SkSurfaceProps* surfaceProps = nullptr,
                                          SkBudgeted = SkBudgeted::kYes);
 
+    /*
+     * This method will attempt to create a drawContext that has, at least, the number of
+     * channels and precision per channel as requested in 'config' (e.g., A8 and 888 can be
+     * converted to 8888). It may also swizzle the channels (e.g., BGRA -> RGBA).
+     * SRGB-ness will be preserved.
+     */
+    sk_sp<GrDrawContext> makeDrawContextWithFallback(
+                                                 SkBackingFit fit,
+                                                 int width, int height,
+                                                 GrPixelConfig config,
+                                                 sk_sp<SkColorSpace> colorSpace,
+                                                 int sampleCnt = 0,
+                                                 GrSurfaceOrigin origin = kDefault_GrSurfaceOrigin,
+                                                 const SkSurfaceProps* surfaceProps = nullptr,
+                                                 SkBudgeted budgeted = SkBudgeted::kYes);
+
     ///////////////////////////////////////////////////////////////////////////
     // Misc.