Re-enable IOSurface Canvas2D.

cc/blink/web_external_texture_layer_impl.cc

Index: cc/blink/web_external_texture_layer_impl.cc
diff --git a/cc/blink/web_external_texture_layer_impl.cc b/cc/blink/web_external_texture_layer_impl.cc
index 03f6e18fb64c45f89b7293d84863c185737b1460..ca33e9f9504bf434d9d8e94f3025292d87b49117 100644
--- a/cc/blink/web_external_texture_layer_impl.cc
+++ b/cc/blink/web_external_texture_layer_impl.cc
@@ -86,9 +86,8 @@ bool WebExternalTextureLayerImpl::PrepareTextureMailbox(
     if (client_mailbox.validSyncToken)
       memcpy(&sync_token, client_mailbox.syncToken, sizeof(sync_token));
 
-    gfx::Size size;
-    if (client_mailbox.allowOverlay)

[danakj, 2016/03/16 01:21:19]

https://code.google.com/p/chromium/codesearch#chromium/src/cc/resources/textu...

Can you explain this change vs that comment?

[erikchen, 2016/03/16 01:33:58]

For other onlookers, the comment says:
"""
// This is valid if allow_overlau() or IsSharedMemory() is true.
gfx::Size size_in_pixels() const { return size_in_pixels_; }
"""

The comment is accurate, in the sense that if either of those conditions is
true, size_in_pixels is guaranteed to be valid. This change does not contradict
the comment.

I see no reason to prematurely drop information, just because the information is
not currently needed. 

[danakj, 2016/03/16 01:48:25]

Well, but what's the point of passing in something valid when nothing can depend
on it? I don't understand why you'd need to change things if nothing is
depending on it incorrectly.

[erikchen, 2016/03/16 01:55:30]

I re-added the conditional """if (client_mailbox.allowOverlay)""".

-      size = gfx::Size(layer_->bounds().width, layer_->bounds().height);
+    gfx::Size size = gfx::Size(client_mailbox.textureSize.width,
+                               client_mailbox.textureSize.height);
 
     *mailbox =
         cc::TextureMailbox(name, sync_token, client_mailbox.textureTarget, size,