cc: Only allow trees created at the current viewport size to draw.

cc/layer_tree_host_impl.cc

Index: cc/layer_tree_host_impl.cc
diff --git a/cc/layer_tree_host_impl.cc b/cc/layer_tree_host_impl.cc
index e357999dcb264deb268a5c190e8f2662127359c6..3cbd76e3bee99e187f1fb0f37f6fd1dc61d89065 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -234,6 +234,10 @@ bool LayerTreeHostImpl::canDraw()
         TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw empty viewport");
         return false;
     }
+    if (deviceViewportSize() != activeTree()->device_viewport_size()) {
+        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw viewport resize incomplete");
+        return false;
+    }
     if (!m_renderer) {
         TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw no renderer");
         return false;
@@ -286,7 +290,7 @@ void LayerTreeHostImpl::startPageScaleAnimation(gfx::Vector2d targetOffset, bool
         scrollTotal.Scale(1 / activeTree()->page_scale_factor());
         scaledScrollableSize.Scale(1 / activeTree()->page_scale_factor());
     }
-    gfx::SizeF viewportSize = gfx::ScaleSize(m_deviceViewportSize, 1 / m_deviceScaleFactor);
+    gfx::SizeF viewportSize = gfx::ScaleSize(deviceViewportSize(), 1 / m_deviceScaleFactor);
 
     double startTimeSeconds = (startTime - base::TimeTicks()).InSecondsF();
     m_pageScaleAnimation = PageScaleAnimation::create(scrollTotal, activeTree()->total_page_scale_factor(), viewportSize, scaledScrollableSize, startTimeSeconds);
@@ -868,7 +872,16 @@ bool LayerTreeHostImpl::swapBuffers()
 
 const gfx::Size& LayerTreeHostImpl::deviceViewportSize() const
 {
-    return m_deviceViewportSize;
+    if (pendingTree())
+        return pendingTree()->device_viewport_size();
+    return activeTree()->device_viewport_size();
+}
+
+const gfx::Size& LayerTreeHostImpl::layoutViewportSize() const
+{
+    if (pendingTree())
+        return pendingTree()->layout_viewport_size();
+    return activeTree()->layout_viewport_size();
 }
 
 const LayerTreeSettings& LayerTreeHostImpl::settings() const
@@ -1091,18 +1104,10 @@ bool LayerTreeHostImpl::initializeRenderer(scoped_ptr<OutputSurface> outputSurfa
 
 void LayerTreeHostImpl::setViewportSize(const gfx::Size& layoutViewportSize, const gfx::Size& deviceViewportSize)
 {
-    if (layoutViewportSize == m_layoutViewportSize && deviceViewportSize == m_deviceViewportSize)
-        return;
-
-    m_layoutViewportSize = layoutViewportSize;
-    m_deviceViewportSize = deviceViewportSize;
-
-    updateMaxScrollOffset();
-
-    if (m_renderer)
-        m_renderer->viewportChanged();
-
-    m_client->onCanDrawStateChanged(canDraw());
+    if (m_settings.implSidePainting)
+        pendingTree()->SetViewportSize(layoutViewportSize, deviceViewportSize);
+    else
+        activeTree()->SetViewportSize(layoutViewportSize, deviceViewportSize);
 }
 
 static void adjustScrollsForPageScaleChange(LayerImpl* layerImpl, float pageScaleChange)
@@ -1428,7 +1433,7 @@ void LayerTreeHostImpl::computePinchZoomDeltas(ScrollAndScaleSet* scrollInfo)
     gfx::Vector2dF scrollEnd = scrollBegin + anchorOffset;
     scrollEnd.Scale(activeTree()->min_page_scale_factor() / scaleBegin);
     scrollEnd -= anchorOffset;
-    scrollEnd.ClampToMax(gfx::RectF(scaledScrollableSize).bottom_right() - gfx::Rect(m_deviceViewportSize).bottom_right());
+    scrollEnd.ClampToMax(gfx::RectF(scaledScrollableSize).bottom_right() - gfx::Rect(deviceViewportSize()).bottom_right());
     scrollEnd.ClampToMin(gfx::Vector2d());
     scrollEnd.Scale(1 / pageScaleDeltaToSend);
     scrollEnd.Scale(m_deviceScaleFactor);
@@ -1718,7 +1723,7 @@ scoped_ptr<base::Value> LayerTreeHostImpl::frameStateAsValue() const
 {
     scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
     state->SetString("lthi_id", StringPrintf("%p", this));
-    state->Set("device_viewport_size", MathUtil::asValue(m_deviceViewportSize).release());
+    state->Set("device_viewport_size", MathUtil::asValue(m_activeTree->device_viewport_size()).release());
     if (m_tileManager)
         state->Set("tiles", m_tileManager->AllTilesAsValue().release());
     return state.PassAs<base::Value>();