Browser Themes: always paint an opaque BG color behind toolbar images

for both the active tab and the toolbar. This matches the bookmarks
bar, i.e. PaintBackgroundAttachedMode.

Bug: 866974
Change-Id: I3a86d2330bf09903f74359e433a4165e3e4d3e8e
Reviewed-on: https://chromium-review.googlesource.com/1171216
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582350}

chrome/browser/ui/views/tabs/tab.cc

@@ -1379,17 +1379,23 @@ void Tab::PaintTabBackgroundFill(gfx::Canvas* canvas,
   const float scale = canvas->UndoDeviceScaleFactor();
 
   canvas->ClipPath(fill_path, true);
+
+  // In the active case, always fill the tab with its bg color first in case the
+  // image is transparent. In the inactive case, the image is guaranteed to be
+  // opaque, so it's only necessary to fill the color when there's no image.
+  if (active || !fill_id) {
+    cc::PaintFlags flags;
+    flags.setAntiAlias(true);
+    flags.setColor(active ? active_color : inactive_color);
+    canvas->DrawRect(gfx::ScaleToEnclosingRect(GetLocalBounds(), scale), flags);
+  }
+
   if (fill_id) {
     gfx::ScopedCanvas scale_scoper(canvas);
     canvas->sk_canvas()->scale(scale, scale);
     canvas->TileImageInt(*GetThemeProvider()->GetImageSkiaNamed(fill_id),
                          GetMirroredX() + background_offset_, 0, 0, y_inset,
                          width(), height());
-  } else {
-    cc::PaintFlags flags;
-    flags.setAntiAlias(true);
-    flags.setColor(active ? active_color : inactive_color);
-    canvas->DrawRect(gfx::ScaleToEnclosingRect(GetLocalBounds(), scale), flags);
   }
 
   if (paint_hover_effect) {

chrome/browser/ui/views/toolbar/toolbar_view.cc

@@ -601,6 +601,11 @@ void ToolbarView::OnPaintBackground(gfx::Canvas* canvas) {
 
   const ui::ThemeProvider* tp = GetThemeProvider();
 
+  // Always fill the toolbar with its bg color first in case the image is
+  // transparent.
+  canvas->FillRect(GetLocalBounds(),
+                   tp->GetColor(ThemeProperties::COLOR_TOOLBAR));
+
   if (tp->HasCustomImage(IDR_THEME_TOOLBAR)) {
     const int x_offset =
         GetMirroredX() + browser_view_->GetMirroredX() +
@@ -610,9 +615,6 @@ void ToolbarView::OnPaintBackground(gfx::Canvas* canvas) {
                          GetLayoutConstant(TABSTRIP_TOOLBAR_OVERLAP);
     canvas->TileImageInt(*tp->GetImageSkiaNamed(IDR_THEME_TOOLBAR), x_offset,
                          y_offset, 0, 0, width(), height());
-  } else {
-    canvas->FillRect(GetLocalBounds(),
-                     tp->GetColor(ThemeProperties::COLOR_TOOLBAR));
   }
 
   // Toolbar/content separator.