CHECKS to catch incorrect PageScaleFactor for OOPIFs.

Since page scale factor should never be non-1.f for OOPIFs, and since
we're seeing this happen anyways, this CL inserts some diagnostic checks
to try and determine where in the page-scale-factor pathways the non-1.f
values are originating.

Bug: 845097
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I1d87e3a618d2fd71aa14cc5149084b08ddb7bf14
Reviewed-on: https://chromium-review.googlesource.com/1110345
Commit-Queue: James MacLean <wjmaclean@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569385}

cc/trees/layer_tree_host.cc

@@ -1130,6 +1130,13 @@ void LayerTreeHost::SetPageScaleFactorAndLimits(float page_scale_factor,
     return;
   DCHECK_GE(page_scale_factor, min_page_scale_factor);
   DCHECK_LE(page_scale_factor, max_page_scale_factor);
+  // We should never process non-unit page_scale_delta for an OOPIF subframe.
+  // TODO(wjmaclean): Remove this check as a pre-condition to closing the bug.
+  // https://crbug.com/845097
+  CHECK(!settings_.is_layer_tree_for_subframe ||
+        page_scale_factor == page_scale_factor_)
+      << "Setting PSF in oopif subframe: old psf = " << page_scale_factor_
+      << ", new psf = " << page_scale_factor;
 
   page_scale_factor_ = page_scale_factor;
   min_page_scale_factor_ = min_page_scale_factor;
@@ -1292,6 +1299,13 @@ bool LayerTreeHost::LayerNeedsPushPropertiesForTesting(Layer* layer) const {
 
 void LayerTreeHost::SetPageScaleFromImplSide(float page_scale) {
   DCHECK(CommitRequested());
+  // We should never process non-unit page_scale_delta for an OOPIF subframe.
+  // TODO(wjmaclean): Remove this check as a pre-condition to closing the bug.
+  // https://crbug.com/845097
+  CHECK(!settings_.is_layer_tree_for_subframe ||
+        page_scale == page_scale_factor_)
+      << "Setting PSF in oopif subframe: old psf = " << page_scale_factor_
+      << ", new psf = " << page_scale;
   page_scale_factor_ = page_scale;
   SetPropertyTreesNeedRebuild();
 }

cc/trees/layer_tree_host_common.cc

@@ -563,6 +563,23 @@ void CalculateDrawPropertiesInternal(
         device_scale_factor_for_page_scale_node = inputs->device_scale_factor;
       }
 
+      // We should never be setting a non-unit page scale factor on an oopif
+      // subframe ... if we attempt this log it and fail.
+      // TODO(wjmaclean): Remove as part of conditions for closing the bug.
+      // https://crbug.com/845097
+      if (inputs->page_scale_factor !=
+              inputs->property_trees->transform_tree.page_scale_factor() &&
+          !inputs->page_scale_transform_node) {
+        LOG(ERROR) << "Setting PageScale on subframe: new psf = "
+                   << inputs->page_scale_factor << ", old psf = "
+                   << inputs->property_trees->transform_tree.page_scale_factor()
+                   << ", in_oopif = "
+                   << inputs->root_layer->layer_tree_impl()
+                          ->settings()
+                          .is_layer_tree_for_subframe;
+        CHECK(false);
+      }
+
       draw_property_utils::UpdatePageScaleFactor(
           inputs->property_trees, inputs->page_scale_transform_node,
           inputs->page_scale_factor, device_scale_factor_for_page_scale_node,

cc/trees/layer_tree_host_impl.cc

@@ -4564,6 +4564,11 @@ std::unique_ptr<ScrollAndScaleSet> LayerTreeHostImpl::ProcessScrollDeltas() {
   CollectScrollbarUpdates(scroll_info.get());
   scroll_info->page_scale_delta =
       active_tree_->page_scale_factor()->PullDeltaForMainThread();
+  // We should never process non-unit page_scale_delta for an OOPIF subframe.
+  // TODO(wjmaclean): Remove this check as a pre-condition to closing the bug.
+  // https://crbug.com/845097
+  CHECK(!settings().is_layer_tree_for_subframe ||
+        scroll_info->page_scale_delta == 1.f);
   scroll_info->top_controls_delta =
       active_tree()->top_controls_shown_ratio()->PullDeltaForMainThread();
   scroll_info->elastic_overscroll_delta =