Move some parts of onReadPixels up to GrGpu readPixels.

src/gpu/GrTest.cpp

Index: src/gpu/GrTest.cpp
diff --git a/src/gpu/GrTest.cpp b/src/gpu/GrTest.cpp
index ce98aa764ba11182a87f2911ea6a900c554b36ec..5420a355e49ab6209b6163ad9ef3513bf3595cc7 100644
--- a/src/gpu/GrTest.cpp
+++ b/src/gpu/GrTest.cpp
@@ -208,7 +208,8 @@ private:
                       int left, int top, int width, int height,
                       GrPixelConfig,
                       void* buffer,
-                      size_t rowBytes) override {
+                      size_t rowBytes,
+                      size_t tightRowBytes) override {
         return false;
     }