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..c88efe6993fb3cb27047681df3cd5a982f7c09e5 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);

[danakj, 2013/02/13 06:51:36]

Is this right? The rootScrollLayer() it's using here is from the active tree. Do
you want the active tree's deviceViewportSize here?

[aelias_OOO_until_Jul13, 2013/02/13 07:37:08]

I definitely want pendingTree size here.  pageScaleAnimations can occur when the
keyboard is brought up (to zoom in tiny text boxes) and we want to zoom in using
the post-keyboard viewport to make sure the textbox is not covered.  I checked
it causes a bug on google.com results page bottom search box if we use
activeTree here.

Probably everything else here should use pendingTree as well although it would
rarely come up... I'd rather not touch it in this patch but I'll file a bug.

 
     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());

[danakj, 2013/02/13 06:51:36]

Should this be the active tree's deviceViewportSize()?

[aelias_OOO_until_Jul13, 2013/02/13 07:37:08]

This is dead code due for deletion, doesn't matter.

     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(deviceViewportSize()).release());

[danakj, 2013/02/13 06:51:36]

This should be the active tree too right?

I feel like the deviceViewportSize() method returning the pending tree sometimes
is inconsistent with other helper methods on LTHImpl and is confusing things
here. It's a nice trick but only gives the right answer in canDraw().

Can you change the *ViewportSize() methods to return the active tree values, and
have canDraw just do the right thing there?

[aelias_OOO_until_Jul13, 2013/02/13 07:37:08]

If it drew a frame, then active tree and pending tree values are the same
anyway.  But OK, this one I'll change to explicit activeTree in case that ever
changes.
I feel the activeTree value is bad and shouldn't be the default.  Things are
already resized throughout the browser process by the time CC hears about it. 
It's not under CC's control like scroll offset or whatnot.  Weird stuff might
happen if we act as though the old viewport size is still good.

     if (m_tileManager)
         state->Set("tiles", m_tileManager->AllTilesAsValue().release());
     return state.PassAs<base::Value>();