gpu: Allow BufferData size=0 for pixel transfer buffer objects.

gpu/command_buffer/client/gles2_implementation.cc

Index: gpu/command_buffer/client/gles2_implementation.cc
diff --git a/gpu/command_buffer/client/gles2_implementation.cc b/gpu/command_buffer/client/gles2_implementation.cc
index 30389fa281a582810a0a090650730048c1a4c846..ec2f7c68c6022198be700192235ca75af7ebaeaa 100644
--- a/gpu/command_buffer/client/gles2_implementation.cc
+++ b/gpu/command_buffer/client/gles2_implementation.cc
@@ -1197,10 +1197,6 @@ void GLES2Implementation::ShaderSource(
 
 void GLES2Implementation::BufferDataHelper(
     GLenum target, GLsizeiptr size, const void* data, GLenum usage) {
-  if (size == 0) {
-    return;
-  }
-
   if (size < 0) {
     SetGLError(GL_INVALID_VALUE, "glBufferData", "size < 0");
     return;
@@ -1230,6 +1226,10 @@ void GLES2Implementation::BufferDataHelper(
     return;
   }
 
+  if (size == 0) {
+    return;
+  }
+
   // If there is no data just send BufferData
   if (!data) {
     helper_->BufferData(target, size, 0, 0, usage);