Compute effective touch action in StyleAdjuster.

third_party/WebKit/Source/core/input/TouchActionUtil.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/input/TouchActionUtil.h"
 
 #include "core/dom/Node.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutObject.h"
@@ skipping 53 matching lines @@
       }
 
       // If we've reached an ancestor that supports panning, stop allowing
       // panning to be disabled.
       if ((layout_object->IsBox() &&
            ToLayoutBox(layout_object)->ScrollsOverflow()) ||
           layout_object->IsLayoutView())
         handled_touch_actions |= TouchAction::kTouchActionPan;
     }
   }
+  // This code is to prevent failure when node does not have a layout object, in

[wkorman, 2017/06/02 03:07:05]

Is this method planned to stay around? I had impression we thought it would go
away once we had the effective touch action in the rare data as is done in the
rest of this change.

If we do need to keep it around this seems like it could be a separate change
and would want its own unit test.

[sunxd, 2017/06/05 20:12:04]

So I'm a little worried about iframe's touch action here and would like to have
some guarding code to test the correctness in the wild, but maybe we can simply
throw the new logic to the wild and revert the patch if anything breaks.

[flackr, 2017/06/07 18:21:47]

Yes, I think this is the right thing to do.

+  // this case, we use the effective_touch_action of its nearest ancestor that

[wkorman, 2017/06/02 03:07:06]

|effective_touch_action| (to make it easier to see var refs vs prose in a
comment)

Or just change to prose ("effective touch action") and rm '_'

[sunxd, 2017/06/05 20:12:04]

Acknowledged.

+  // has a layout object.
+  TouchAction precomputed_touch_action;
+  for (const Node* cur_node = &node; cur_node;
+       cur_node = ParentNodeAcrossFrames(cur_node)) {
+    if (cur_node->GetLayoutObject()) {
+      precomputed_touch_action =
+          cur_node->GetLayoutObject()->Style()->GetEffectiveTouchAction();
+      break;
+    }
+  }
+  DCHECK_EQ(effective_touch_action, precomputed_touch_action);
   return effective_touch_action;
 }
 
 }  // namespace TouchActionUtil
 }  // namespace blink