Don't hide pinch viewport scrollbars near min-scale with device emulation.

Depends on http://crrev.com/1269813004.

BUG=515746
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1267603004

Cr-Commit-Position: refs/heads/master@{#341784}

7 files changed, 33 insertions, 18 deletions

diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 179d34c..4d72eb2 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -101,6 +101,7 @@ LayerTreeHost::LayerTreeHost(InitParams* params)
       top_controls_shrink_blink_size_(false),
       top_controls_height_(0.f),
       top_controls_shown_ratio_(0.f),
+      hide_pinch_scrollbars_near_min_scale_(false),
       device_scale_factor_(1.f),
       visible_(true),
       page_scale_factor_(1.f),
@@ -301,6 +302,10 @@ void LayerTreeHost::FinishCommitOnImplThread(LayerTreeHostImpl* host_impl) {
 
   // Setting property trees must happen before pushing the page scale.
   sync_tree->SetPropertyTrees(property_trees_);
+
+  sync_tree->set_hide_pinch_scrollbars_near_min_scale(
+      hide_pinch_scrollbars_near_min_scale_);
+
   sync_tree->PushPageScaleFromMainThread(
       page_scale_factor_, min_page_scale_factor_, max_page_scale_factor_);
   sync_tree->elastic_overscroll()->PushFromMainThread(elastic_overscroll_);
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index 8015c34..c04e8e7 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -211,6 +211,10 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
   void SetTopControlsHeight(float height, bool shrink);
   void SetTopControlsShownRatio(float ratio);
 
+  void set_hide_pinch_scrollbars_near_min_scale(bool hide) {
+    hide_pinch_scrollbars_near_min_scale_ = hide;
+  }
+
   gfx::Size device_viewport_size() const { return device_viewport_size_; }
 
   void ApplyPageScaleDeltaFromImplSide(float page_scale_delta);
@@ -443,6 +447,7 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
   bool top_controls_shrink_blink_size_;
   float top_controls_height_;
   float top_controls_shown_ratio_;
+  bool hide_pinch_scrollbars_near_min_scale_;
   float device_scale_factor_;
 
   bool visible_;
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 1996302..aba949e 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -58,6 +58,7 @@ LayerTreeImpl::LayerTreeImpl(
       page_scale_factor_(page_scale_factor),
       min_page_scale_factor_(0),
       max_page_scale_factor_(0),
+      hide_pinch_scrollbars_near_min_scale_(false),
       elastic_overscroll_(elastic_overscroll),
       viewport_size_invalid_(false),
       needs_update_draw_properties_(true),
@@ -230,6 +231,9 @@ void LayerTreeImpl::PushPropertiesTo(LayerTreeImpl* target_tree) {
   target_tree->set_top_controls_height(top_controls_height_);
   target_tree->PushTopControls(nullptr);
 
+  target_tree->set_hide_pinch_scrollbars_near_min_scale(
+      hide_pinch_scrollbars_near_min_scale_);
+
   // Active tree already shares the page_scale_factor object with pending
   // tree so only the limits need to be provided.
   target_tree->PushPageScaleFactorAndLimits(nullptr, min_page_scale_factor(),
@@ -465,11 +469,10 @@ void LayerTreeImpl::DidUpdatePageScale() {
   }
 
   ForceScrollbarParameterUpdateAfterScaleChange(PageScaleLayer());
-
-  HideInnerViewportScrollbarsIfNearMinimumScale();
+  HideInnerViewportScrollbarsIfNeeded();
 }
 
-void LayerTreeImpl::HideInnerViewportScrollbarsIfNearMinimumScale() {
+void LayerTreeImpl::HideInnerViewportScrollbarsIfNeeded() {
   if (!InnerViewportContainerLayer())
     return;
 
@@ -479,15 +482,14 @@ void LayerTreeImpl::HideInnerViewportScrollbarsIfNearMinimumScale() {
   if (!scrollbars)
     return;
 
+  float minimum_scale_to_show_at = min_page_scale_factor() * 1.05f;
+  bool hide_scrollbars =
+      hide_pinch_scrollbars_near_min_scale_ &&
+      (current_page_scale_factor() < minimum_scale_to_show_at);
+
   for (LayerImpl::ScrollbarSet::iterator it = scrollbars->begin();
-       it != scrollbars->end();
-       ++it) {
-    ScrollbarLayerImplBase* scrollbar = *it;
-    float minimum_scale_to_show_at =
-        min_page_scale_factor() * settings().scrollbar_show_scale_threshold;
-    scrollbar->SetHideLayerAndSubtree(
-        current_page_scale_factor() < minimum_scale_to_show_at);
-  }
+       it != scrollbars->end(); ++it)
+    (*it)->SetHideLayerAndSubtree(hide_scrollbars);
 }
 
 SyncedProperty<ScaleGroup>* LayerTreeImpl::page_scale_factor() {
@@ -543,7 +545,7 @@ void LayerTreeImpl::SetViewportLayersFromIds(
   inner_viewport_scroll_layer_id_ = inner_viewport_scroll_layer_id;
   outer_viewport_scroll_layer_id_ = outer_viewport_scroll_layer_id;
 
-  HideInnerViewportScrollbarsIfNearMinimumScale();
+  HideInnerViewportScrollbarsIfNeeded();
 }
 
 void LayerTreeImpl::ClearViewportLayers() {
diff --git a/cc/trees/layer_tree_impl.h b/cc/trees/layer_tree_impl.h
index 476d8aa..afd4dfa 100644
--- a/cc/trees/layer_tree_impl.h
+++ b/cc/trees/layer_tree_impl.h
@@ -198,6 +198,10 @@ class CC_EXPORT LayerTreeImpl {
   SyncedProperty<ScaleGroup>* page_scale_factor();
   const SyncedProperty<ScaleGroup>* page_scale_factor() const;
 
+  void set_hide_pinch_scrollbars_near_min_scale(bool hide) {
+    hide_pinch_scrollbars_near_min_scale_ = hide;
+  }
+
   SyncedElasticOverscroll* elastic_overscroll() {
     return elastic_overscroll_.get();
   }
@@ -392,7 +396,7 @@ class CC_EXPORT LayerTreeImpl {
   bool SetPageScaleFactorLimits(float min_page_scale_factor,
                                 float max_page_scale_factor);
   void DidUpdatePageScale();
-  void HideInnerViewportScrollbarsIfNearMinimumScale();
+  void HideInnerViewportScrollbarsIfNeeded();
   void PushTopControls(const float* top_controls_shown_ratio);
   LayerTreeHostImpl* layer_tree_host_impl_;
   int source_frame_number_;
@@ -414,6 +418,7 @@ class CC_EXPORT LayerTreeImpl {
   scoped_refptr<SyncedProperty<ScaleGroup>> page_scale_factor_;
   float min_page_scale_factor_;
   float max_page_scale_factor_;
+  bool hide_pinch_scrollbars_near_min_scale_;
 
   scoped_refptr<SyncedElasticOverscroll> elastic_overscroll_;
 
diff --git a/cc/trees/layer_tree_impl_unittest.cc b/cc/trees/layer_tree_impl_unittest.cc
index 9e8fee5..5681418 100644
--- a/cc/trees/layer_tree_impl_unittest.cc
+++ b/cc/trees/layer_tree_impl_unittest.cc
@@ -25,7 +25,6 @@ class LayerTreeImplTest : public LayerTreeHostCommonTest {
   LayerTreeImplTest() {
     LayerTreeSettings settings;
     settings.layer_transforms_should_scale_layer_contents = true;
-    settings.scrollbar_show_scale_threshold = 1.1f;
     host_impl_.reset(new FakeLayerTreeHostImpl(
         settings, &proxy_, &shared_bitmap_manager_, &task_graph_runner_));
     EXPECT_TRUE(host_impl_->InitializeRenderer(FakeOutputSurface::Create3d()));
@@ -1296,6 +1295,7 @@ TEST_F(LayerTreeImplTest, MakeScrollbarsInvisibleNearMinPageScale) {
   const bool kIsOverlayScrollbar = true;
 
   LayerTreeImpl* active_tree = host_impl().active_tree();
+  active_tree->set_hide_pinch_scrollbars_near_min_scale(true);
 
   scoped_ptr<LayerImpl> scroll_layer = LayerImpl::Create(active_tree, 1);
   scoped_ptr<SolidColorScrollbarLayerImpl> vertical_scrollbar_layer =
@@ -1343,11 +1343,11 @@ TEST_F(LayerTreeImplTest, MakeScrollbarsInvisibleNearMinPageScale) {
   EXPECT_TRUE(vertical_scrollbar_layer->hide_layer_and_subtree());
   EXPECT_TRUE(horizontal_scrollbar_layer->hide_layer_and_subtree());
 
-  active_tree->PushPageScaleFromMainThread(1.05f, 1.0f, 4.0f);
+  active_tree->PushPageScaleFromMainThread(1.04f, 1.0f, 4.0f);
   EXPECT_TRUE(vertical_scrollbar_layer->hide_layer_and_subtree());
   EXPECT_TRUE(horizontal_scrollbar_layer->hide_layer_and_subtree());
 
-  active_tree->PushPageScaleFromMainThread(1.1f, 1.0f, 4.0f);
+  active_tree->PushPageScaleFromMainThread(1.06f, 1.0f, 4.0f);
   EXPECT_FALSE(vertical_scrollbar_layer->hide_layer_and_subtree());
   EXPECT_FALSE(horizontal_scrollbar_layer->hide_layer_and_subtree());
 
diff --git a/cc/trees/layer_tree_settings.cc b/cc/trees/layer_tree_settings.cc
index 2a2d92b..0869e92 100644
--- a/cc/trees/layer_tree_settings.cc
+++ b/cc/trees/layer_tree_settings.cc
@@ -36,7 +36,6 @@ LayerTreeSettings::LayerTreeSettings()
       scrollbar_fade_delay_ms(0),
       scrollbar_fade_resize_delay_ms(0),
       scrollbar_fade_duration_ms(0),
-      scrollbar_show_scale_threshold(1.0f),
       solid_color_scrollbar_color(SK_ColorWHITE),
       timeout_and_draw_when_animation_checkerboards(true),
       layer_transforms_should_scale_layer_contents(false),
diff --git a/cc/trees/layer_tree_settings.h b/cc/trees/layer_tree_settings.h
index 4820aca..27e80af 100644
--- a/cc/trees/layer_tree_settings.h
+++ b/cc/trees/layer_tree_settings.h
@@ -51,7 +51,6 @@ class CC_EXPORT LayerTreeSettings {
   int scrollbar_fade_delay_ms;
   int scrollbar_fade_resize_delay_ms;
   int scrollbar_fade_duration_ms;
-  float scrollbar_show_scale_threshold;
   SkColor solid_color_scrollbar_color;
   bool timeout_and_draw_when_animation_checkerboards;
   bool layer_transforms_should_scale_layer_contents;