Return an Error from Framebuffer::syncState.

This pipes errors up from the Impl to the top level. There are
still a few places were error swallowing is needed, because the
Framebuffer API doesn't support returning an error.

Bug: angleproject:2372
Change-Id: Idc06bda1817fd28075940f69874d8b6ba69194f9
Reviewed-on: https://chromium-review.googlesource.com/954290
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Luc Ferron <lucferron@chromium.org>
diff --git a/src/libANGLE/renderer/FramebufferImpl_mock.h b/src/libANGLE/renderer/FramebufferImpl_mock.h
index c2d0696..358b06a 100644
--- a/src/libANGLE/renderer/FramebufferImpl_mock.h
+++ b/src/libANGLE/renderer/FramebufferImpl_mock.h
@@ -50,7 +50,7 @@
 
     MOCK_CONST_METHOD1(checkStatus, bool(const gl::Context *));
 
-    MOCK_METHOD2(syncState, void(const gl::Context *, const gl::Framebuffer::DirtyBits &));
+    MOCK_METHOD2(syncState, gl::Error(const gl::Context *, const gl::Framebuffer::DirtyBits &));
 
     MOCK_METHOD0(destructor, void());
 };