Re-enable two tests in scrollbar_unittest.cc, fix rounding precision loss in base_scroll_bar.cc

Change-Id: I6d2fcdf455cb65faa67450754b8fea4084783afb
Reviewed-on: https://chromium-review.googlesource.com/c/1340957
Commit-Queue: Ryan Meier <rameier@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610133}

ui/views/controls/scrollbar/base_scroll_bar.cc

@@ -84,8 +84,8 @@ void BaseScrollBar::ScrollByAmount(ScrollAmount amount) {
 
 void BaseScrollBar::ScrollToThumbPosition(int thumb_position,
                                           bool scroll_to_middle) {
-  contents_scroll_offset_ =
-      CalculateContentsOffset(thumb_position, scroll_to_middle);
+  contents_scroll_offset_ = CalculateContentsOffset(
+      static_cast<float>(thumb_position), scroll_to_middle);
   if (contents_scroll_offset_ < GetMinPosition()) {
     contents_scroll_offset_ = GetMinPosition();
   } else if (contents_scroll_offset_ > GetMaxPosition()) {
@@ -460,16 +460,17 @@ int BaseScrollBar::CalculateThumbPosition(int contents_scroll_offset) const {
          (contents_size_ - viewport_size_);
 }
 
-int BaseScrollBar::CalculateContentsOffset(int thumb_position,
+int BaseScrollBar::CalculateContentsOffset(float thumb_position,
                                            bool scroll_to_middle) const {
-  int thumb_size = thumb_->GetSize();
+  float thumb_size = static_cast<float>(thumb_->GetSize());
   int track_size = GetTrackSize();
   if (track_size == thumb_size)
     return 0;
   if (scroll_to_middle)
     thumb_position = thumb_position - (thumb_size / 2);
-  return (thumb_position * (contents_size_ - viewport_size_)) /
-         (track_size - thumb_size);
+  float result = (thumb_position * (contents_size_ - viewport_size_)) /
+                 (track_size - thumb_size);
+  return static_cast<int>(result);
 }
 
 }  // namespace views

ui/views/controls/scrollbar/base_scroll_bar.h

@@ -135,7 +135,7 @@ class VIEWS_EXPORT BaseScrollBar : public ScrollBar,
   // Calculates the current value of the contents offset (contents coordinates)
   // based on the current thumb position (thumb track coordinates). See
   // |ScrollToThumbPosition| for an explanation of |scroll_to_middle|.
-  int CalculateContentsOffset(int thumb_position,
+  int CalculateContentsOffset(float thumb_position,
                               bool scroll_to_middle) const;
 
   // Called when the state of the thumb track changes (e.g. by the user

ui/views/controls/scrollbar/scrollbar_unittest.cc

@@ -87,17 +87,7 @@ class ScrollBarViewsTest : public ViewsTestBase {
   std::unique_ptr<TestScrollBarController> controller_;
 };
 
-// TODO(dnicoara) Can't run the test on Windows since the scrollbar |Part|
-// isn't handled in NativeTheme.
-#if defined(OS_WIN)
-#define MAYBE_Scrolling DISABLED_Scrolling
-#define MAYBE_ScrollBarFitsToBottom DISABLED_ScrollBarFitsToBottom
-#else
-#define MAYBE_Scrolling Scrolling
-#define MAYBE_ScrollBarFitsToBottom ScrollBarFitsToBottom
-#endif
-
-TEST_F(ScrollBarViewsTest, MAYBE_Scrolling) {
+TEST_F(ScrollBarViewsTest, Scrolling) {
   EXPECT_EQ(0, scrollbar_->GetPosition());
   EXPECT_EQ(900, scrollbar_->GetMaxPosition());
   EXPECT_EQ(0, scrollbar_->GetMinPosition());
@@ -135,7 +125,7 @@ TEST_F(ScrollBarViewsTest, MAYBE_Scrolling) {
   EXPECT_EQ(0, controller_->last_position);
 }
 
-TEST_F(ScrollBarViewsTest, MAYBE_ScrollBarFitsToBottom) {
+TEST_F(ScrollBarViewsTest, ScrollBarFitsToBottom) {
   scrollbar_->Update(100, 1999, 0);
   EXPECT_EQ(0, scrollbar_->GetPosition());
   EXPECT_EQ(1899, scrollbar_->GetMaxPosition());