When GL_RGBA readPixels are slow do swizzle using a draw then readPixels with GL_BGRA

Review URL: http://codereview.appspot.com/5339051/


git-svn-id: http://skia.googlecode.com/svn/trunk@2631 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/GrGLConfig_chrome.h b/include/gpu/GrGLConfig_chrome.h
index d21e2f4..79324ab 100644
--- a/include/gpu/GrGLConfig_chrome.h
+++ b/include/gpu/GrGLConfig_chrome.h
@@ -14,6 +14,9 @@
 // ANGLE creates a temp VB for vertex attributes not specified per-vertex.
 #define GR_GL_NO_CONSTANT_ATTRIBUTES    GR_WIN32_BUILD
 
+// RGBA Readbacks are a slow path in ANGLE
+#define GR_GL_RGBA_8888_READBACK_SLOW   GR_WIN32_BUILD
+
 // cmd buffer allocates memory and memsets it to zero when it sees glBufferData
 // with NULL.
 #define GR_GL_USE_BUFFER_DATA_NULL_HINT 0