Reland Change minimum length of Aura overlay scrollbars.

third_party/WebKit/Source/web/tests/ScrollbarsTest.cpp

Index: third_party/WebKit/Source/web/tests/ScrollbarsTest.cpp
diff --git a/third_party/WebKit/Source/web/tests/ScrollbarsTest.cpp b/third_party/WebKit/Source/web/tests/ScrollbarsTest.cpp
index eee9d25621738eb0c628ed40bede8ff32fd0bc23..a97e23189a1e5c67ac13a5393abe715013f503f2 100644
--- a/third_party/WebKit/Source/web/tests/ScrollbarsTest.cpp
+++ b/third_party/WebKit/Source/web/tests/ScrollbarsTest.cpp
@@ -2,10 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "core/frame/FrameView.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/PaintLayerScrollableArea.h"
 #include "platform/testing/RuntimeEnabledFeaturesTestHelpers.h"
+#include "platform/testing/TestingPlatformSupport.h"
 #include "platform/testing/UnitTestHelpers.h"
+#include "public/platform/WebThemeEngine.h"
 #include "public/web/WebScriptSource.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "web/WebLocalFrameImpl.h"
@@ -42,6 +45,76 @@ TEST_F(ScrollbarsTest, DocumentStyleRecalcPreservesScrollbars) {
   ASSERT_TRUE(plsa->verticalScrollbar() && plsa->horizontalScrollbar());
 }
 
+typedef bool TestParamOverlayScrollbar;
+class ScrollbarAppearanceTest
+    : public SimTest,
+      public ::testing::WithParamInterface<TestParamOverlayScrollbar> {
+ public:
+  // Use real scrollbars to ensure we're testing the real ScrollbarThemes.
+  ScrollbarAppearanceTest() : m_mockScrollbars(false, GetParam()) {}
+
+ private:
+  FrameTestHelpers::UseMockScrollbarSettings m_mockScrollbars;
+};
+
+class StubWebThemeEngine : public WebThemeEngine {
+ public:
+  WebSize getSize(Part part) override {
+    switch (part) {
+      case PartScrollbarHorizontalThumb:
+        return blink::WebSize(kMinimumHorizontalLength, 15);
+      case PartScrollbarVerticalThumb:
+        return blink::WebSize(15, kMinimumVerticalLength);
+      default:
+        return WebSize();
+    }
+  }
+  static constexpr int kMinimumHorizontalLength = 51;
+  static constexpr int kMinimumVerticalLength = 52;
+};
+
+constexpr int StubWebThemeEngine::kMinimumHorizontalLength;
+constexpr int StubWebThemeEngine::kMinimumVerticalLength;
+
+class ScrollbarTestingPlatformSupport : public TestingPlatformSupport {
+ public:
+  WebThemeEngine* themeEngine() override { return &m_stubThemeEngine; }
+
+ private:
+  StubWebThemeEngine m_stubThemeEngine;
+};
+
+// Test both overlay and non-overlay scrollbars.
+INSTANTIATE_TEST_CASE_P(All, ScrollbarAppearanceTest, ::testing::Bool());
+
+#if !OS(MACOSX)
+// Ensure that the minimum length for a scrollbar thumb comes from the
+// WebThemeEngine. Note, Mac scrollbars differ from all other platforms so this
+// test doesn't apply there. https://crbug.com/682209.
+TEST_P(ScrollbarAppearanceTest, ThemeEngineDefinesMinimumThumbLength) {
+  ScopedTestingPlatformSupport<ScrollbarTestingPlatformSupport> platform;
+
+  v8::HandleScope handleScope(v8::Isolate::GetCurrent());
+  webView().resize(WebSize(800, 600));
+  SimRequest request("https://example.com/test.html", "text/html");
+  loadURL("https://example.com/test.html");
+  request.complete(
+      "<style> body { width: 1000000px; height: 1000000px; } </style>");
+  ScrollableArea* scrollableArea =
+      document().view()->layoutViewportScrollableArea();
+
+  compositor().beginFrame();
+  ASSERT_TRUE(scrollableArea->verticalScrollbar());
+  ASSERT_TRUE(scrollableArea->horizontalScrollbar());
+
+  ScrollbarTheme& theme = scrollableArea->verticalScrollbar()->theme();
+  EXPECT_EQ(StubWebThemeEngine::kMinimumHorizontalLength,
+            theme.thumbLength(*scrollableArea->horizontalScrollbar()));
+  EXPECT_EQ(StubWebThemeEngine::kMinimumVerticalLength,
+            theme.thumbLength(*scrollableArea->verticalScrollbar()));
+}
+#endif
+
 }  // namespace
 
 }  // namespace blink