Made double-tap zoom work in pinch virtual viewport mode (Chromium-side).

cc/trees/layer_tree_host.cc

 // Copyright 2011 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 "cc/trees/layer_tree_host.h"
 
 #include <algorithm>
 #include <stack>
 #include <string>
 
@@ skipping 1073 matching lines @@
     }
   }
 
   if (!inner_viewport_scroll_delta.IsZero() ||
       !outer_viewport_scroll_delta.IsZero() ||
       info->page_scale_delta != 1.f ||
       info->top_controls_delta) {
     // SetScrollOffsetFromImplSide above could have destroyed the tree,
     // so re-get this layer before doing anything to it.
 
+    DCHECK(inner_viewport_scroll_layer_.get());  // We should always have this.
+
     // Preemptively apply the scroll offset and scale delta here before sending
     // it to the client.  If the client comes back and sets it to the same
     // value, then the layer can early out without needing a full commit.
-    DCHECK(inner_viewport_scroll_layer_.get());  // We should always have this.
-
     inner_viewport_scroll_layer_->SetScrollOffsetFromImplSide(
         inner_viewport_scroll_layer_->scroll_offset() +
         inner_viewport_scroll_delta);
     if (outer_viewport_scroll_layer_.get()) {
       outer_viewport_scroll_layer_->SetScrollOffsetFromImplSide(
           outer_viewport_scroll_layer_->scroll_offset() +
           outer_viewport_scroll_delta);
     }
+
     ApplyPageScaleDeltaFromImplSide(info->page_scale_delta);
-
-    client_->ApplyViewportDeltas(
-        inner_viewport_scroll_delta + outer_viewport_scroll_delta,
-        info->page_scale_delta,
-        info->top_controls_delta);
+    if (!outer_viewport_scroll_layer_.get()) {
+      client_->ApplyViewportDeltas(
+          inner_viewport_scroll_delta + outer_viewport_scroll_delta,
+          info->page_scale_delta,
+          info->top_controls_delta);
+    } else {
+      client_->ApplyViewportDeltas(
+          inner_viewport_scroll_delta,
+          outer_viewport_scroll_delta,
+          info->page_scale_delta,
+          info->top_controls_delta);
+    }
   }
 }
 
 void LayerTreeHost::StartRateLimiter() {
   if (inside_begin_main_frame_)
     return;
 
   if (!rate_limit_timer_.IsRunning()) {
     rate_limit_timer_.Start(FROM_HERE,
                             base::TimeDelta(),
@@ skipping 194 matching lines @@
   swap_promise_list_.push_back(swap_promise.Pass());
 }
 
 void LayerTreeHost::BreakSwapPromises(SwapPromise::DidNotSwapReason reason) {
   for (size_t i = 0; i < swap_promise_list_.size(); i++)
     swap_promise_list_[i]->DidNotSwap(reason);
   swap_promise_list_.clear();
 }
 
 }  // namespace cc