Rename flushForExternalRead->flushForExternalIO and always call in SkSurface::getTextureHandle

src/image/SkSurface_Gpu.cpp

Index: src/image/SkSurface_Gpu.cpp
diff --git a/src/image/SkSurface_Gpu.cpp b/src/image/SkSurface_Gpu.cpp
index 71bed3a9b9083a70bbc1afc9603f61df66ee0ea5..d243b657b4eddf93c403187983f284b1ab502cbc 100644
--- a/src/image/SkSurface_Gpu.cpp
+++ b/src/image/SkSurface_Gpu.cpp
@@ -30,15 +30,14 @@ GrBackendObject SkSurface_Gpu::onGetTextureHandle(TextureHandleAccess access) {
     GrRenderTarget* rt = fDevice->accessRenderTarget();
     switch (access) {
         case kFlushRead_TextureHandleAccess:
-            rt->prepareForExternalRead();   // todo: rename to prepareForExternalAccess()
             break;
         case kFlushWrite_TextureHandleAccess:
         case kDiscardWrite_TextureHandleAccess:
             // for now we don't special-case on Discard, but we may in the future.
             this->notifyContentWillChange(kRetain_ContentChangeMode);
-            rt->flushWrites();
             break;
     }
+    rt->prepareForExternalIO();
     return rt->asTexture()->getTextureHandle();
 }