cc: Fix a bug of preventing conversion from non-tiled mask to tiled mask.

In a previous mask tiling patch, there was a typo that incorrectly check
mask type when doing the tiled/non-tiled conversion.

This does not break anything as currently the flag is disabled. This
patch fixes this typo.

BUG=567293
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2809653002
Cr-Commit-Position: refs/heads/master@{#463325}

cc/layers/picture_layer.cc

@@ -149,7 +149,7 @@ void PictureLayer::SetLayerMaskType(LayerMaskType mask_type) {
   // We do not allow converting SINGLE_TEXTURE_MASK to MULTI_TEXTURE_MASK in
   // order to avoid rerastering when a mask's transform is being animated.
   if (mask_type_ == LayerMaskType::SINGLE_TEXTURE_MASK &&
-      LayerMaskType::MULTI_TEXTURE_MASK)
+      mask_type == LayerMaskType::MULTI_TEXTURE_MASK)
     return;
   mask_type_ = mask_type;
 }