Fix CSSFlexibleBox use counter

Until now CSSFlexibleBox use counter was counting
not only "display: flex|inline-flex" elements,
but also buttons or any other classes that inherit
from LayoutFlexbibleBox:
That's an implementation detail and we shouldn't be interested
in counting those cases as flexbox usage.

The patch moves the counter to LayoutObject::CreateObject()
so we actually check the display value.
The patch also moves the grid layout counter,
despite nobody is inheriting from LayoutGrid now,
a similar issue could happen in the future if someone does it.

New unit tests are added to verify that things are working
as expected now.

Change-Id: I716870a666a4167d19153667bc80f68a3ba0d7e3
Reviewed-on: https://chromium-review.googlesource.com/c/1273107
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598791}

third_party/blink/renderer/core/frame/use_counter_test.cc

@@ -321,6 +321,46 @@ TEST_F(UseCounterTest, CSSGridLayoutPercentageRowIndefiniteHeight) {
   EXPECT_TRUE(UseCounter::IsCounted(document, feature));
 }
 
+TEST_F(UseCounterTest, CSSFlexibleBox) {
+  std::unique_ptr<DummyPageHolder> dummy_page_holder =
+      DummyPageHolder::Create(IntSize(800, 600));
+  Page::InsertOrdinaryPageForTesting(&dummy_page_holder->GetPage());
+  Document& document = dummy_page_holder->GetDocument();
+  WebFeature feature = WebFeature::kCSSFlexibleBox;
+  EXPECT_FALSE(UseCounter::IsCounted(document, feature));
+  document.documentElement()->SetInnerHTMLFromString(
+      "<div style='display: flex;'>flexbox</div>");
+  document.View()->UpdateAllLifecyclePhases();
+  EXPECT_TRUE(UseCounter::IsCounted(document, feature));
+}
+
+TEST_F(UseCounterTest, CSSFlexibleBoxInline) {
+  std::unique_ptr<DummyPageHolder> dummy_page_holder =
+      DummyPageHolder::Create(IntSize(800, 600));
+  Page::InsertOrdinaryPageForTesting(&dummy_page_holder->GetPage());
+  Document& document = dummy_page_holder->GetDocument();
+  WebFeature feature = WebFeature::kCSSFlexibleBox;
+  EXPECT_FALSE(UseCounter::IsCounted(document, feature));
+  document.documentElement()->SetInnerHTMLFromString(
+      "<div style='display: inline-flex;'>flexbox</div>");
+  document.View()->UpdateAllLifecyclePhases();
+  EXPECT_TRUE(UseCounter::IsCounted(document, feature));
+}
+
+TEST_F(UseCounterTest, CSSFlexibleBoxButton) {
+  // LayoutButton is a subclass of LayoutFlexibleBox, however we don't want it
+  // to be counted as usage of flexboxes as it's an implementation detail.
+  std::unique_ptr<DummyPageHolder> dummy_page_holder =
+      DummyPageHolder::Create(IntSize(800, 600));
+  Page::InsertOrdinaryPageForTesting(&dummy_page_holder->GetPage());
+  Document& document = dummy_page_holder->GetDocument();
+  WebFeature feature = WebFeature::kCSSFlexibleBox;
+  EXPECT_FALSE(UseCounter::IsCounted(document, feature));
+  document.documentElement()->SetInnerHTMLFromString("<button>button</button>");
+  document.View()->UpdateAllLifecyclePhases();
+  EXPECT_FALSE(UseCounter::IsCounted(document, feature));
+}
+
 class DeprecationTest : public testing::Test {
  public:
   DeprecationTest()

third_party/blink/renderer/core/layout/layout_flexible_box.cc

@@ -60,8 +60,6 @@ LayoutFlexibleBox::LayoutFlexibleBox(Element* element)
       has_definite_height_(SizeDefiniteness::kUnknown),
       in_layout_(false) {
   DCHECK(!ChildrenInline());
-  if (!IsAnonymous())
-    UseCounter::Count(GetDocument(), WebFeature::kCSSFlexibleBox);
 }
 
 LayoutFlexibleBox::~LayoutFlexibleBox() = default;

third_party/blink/renderer/core/layout/layout_grid.cc

@@ -49,8 +49,6 @@ LayoutGrid::LayoutGrid(Element* element)
       grid_(Grid::Create(this)),
       track_sizing_algorithm_(this, *grid_) {
   DCHECK(!ChildrenInline());
-  if (!IsAnonymous())
-    UseCounter::Count(GetDocument(), WebFeature::kCSSGridLayout);
 }
 
 LayoutGrid::~LayoutGrid() = default;

third_party/blink/renderer/core/layout/layout_object.cc

@@ -268,9 +268,11 @@ LayoutObject* LayoutObject::CreateObject(Element* element,
       return new LayoutDeprecatedFlexibleBox(*element);
     case EDisplay::kFlex:
     case EDisplay::kInlineFlex:
+      UseCounter::Count(element->GetDocument(), WebFeature::kCSSFlexibleBox);
       return LayoutObjectFactory::CreateFlexibleBox(*element, style);
     case EDisplay::kGrid:
     case EDisplay::kInlineGrid:
+      UseCounter::Count(element->GetDocument(), WebFeature::kCSSGridLayout);
       return new LayoutGrid(element);
     case EDisplay::kLayoutCustom:
     case EDisplay::kInlineLayoutCustom: