Widget::ShouldUseNativeFrame is now meaningful on Linux.

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

Index: chrome/browser/ui/views/tabs/tab_strip.cc
diff --git a/chrome/browser/ui/views/tabs/tab_strip.cc b/chrome/browser/ui/views/tabs/tab_strip.cc
index a33da5211fe38f5b2a5cd5e5c06a7cf31fd3b5b1..056c6a00672945b290b781ad103686b8d1d84bd8 100644
--- a/chrome/browser/ui/views/tabs/tab_strip.cc
+++ b/chrome/browser/ui/views/tabs/tab_strip.cc
@@ -70,9 +70,11 @@ namespace {
 static const int kTabStripAnimationVSlop = 40;
 // Inactive tabs in a native frame are slightly transparent.
 static const int kNativeFrameInactiveTabAlpha = 200;
+#if defined(OS_WIN)
 // If there are multiple tabs selected then make non-selected inactive tabs
 // even more transparent.
 static const int kNativeFrameInactiveTabAlphaMultiSelection = 150;

[sky, 2014/02/03 21:53:03]

Rename this to better match other naming.

[Matt Giuca, 2014/02/05 23:25:31]

Done.

+#endif
 
 // Alpha applied to all elements save the selected tabs.
 static const int kInactiveTabAndNewTabButtonAlphaAsh = 230;
@@ -333,7 +335,9 @@ class NewTabButton : public views::ImageButton {
   virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE;
 
  private:
-  bool ShouldUseNativeFrame() const;
+  // Returns true on Windows if the Glass styling is being used.
+  // This implies that the tab strip overlaps a native window frame.
+  bool UsingWindowsGlass() const;
   gfx::ImageSkia GetBackgroundImage(views::CustomButton::ButtonState state,
                                     ui::ScaleFactor scale_factor) const;
   gfx::ImageSkia GetImageForState(views::CustomButton::ButtonState state,
@@ -427,16 +431,19 @@ void NewTabButton::OnGestureEvent(ui::GestureEvent* event) {
   event->SetHandled();
 }
 
-bool NewTabButton::ShouldUseNativeFrame() const {
+bool NewTabButton::UsingWindowsGlass() const {
+#if defined(OS_WIN)
   return GetWidget() &&
     GetWidget()->GetTopLevelWidget()->ShouldUseNativeFrame();
+#endif
+return false;
 }
 
 gfx::ImageSkia NewTabButton::GetBackgroundImage(
     views::CustomButton::ButtonState state,
     ui::ScaleFactor scale_factor) const {
   int background_id = 0;
-  if (ShouldUseNativeFrame()) {
+  if (UsingWindowsGlass()) {
     background_id = IDR_THEME_TAB_BACKGROUND_V;
   } else if (tab_strip_->controller()->IsIncognito()) {
     background_id = IDR_THEME_TAB_BACKGROUND_INCOGNITO;
@@ -452,7 +459,7 @@ gfx::ImageSkia NewTabButton::GetBackgroundImage(
   switch (state) {
     case views::CustomButton::STATE_NORMAL:
     case views::CustomButton::STATE_HOVERED:
-      alpha = ShouldUseNativeFrame() ? kNativeFrameInactiveTabAlpha : 255;
+      alpha = UsingWindowsGlass() ? kNativeFrameInactiveTabAlpha : 255;
       break;
     case views::CustomButton::STATE_PRESSED:
       alpha = 145;
@@ -525,7 +532,7 @@ gfx::ImageSkia NewTabButton::GetImageForState(
   // Draw the button border with a slight alpha.
   const int kNativeFrameOverlayAlpha = 178;

[sky, 2014/02/03 21:53:03]

rename these too.

[Matt Giuca, 2014/02/05 23:25:31]

Done.

   const int kOpaqueFrameOverlayAlpha = 230;
-  uint8 alpha = ShouldUseNativeFrame() ?
+  uint8 alpha = UsingWindowsGlass() ?
       kNativeFrameOverlayAlpha : kOpaqueFrameOverlayAlpha;
   canvas.DrawImageInt(*overlay, 0, 0, alpha);
 
@@ -1332,7 +1339,9 @@ void TabStrip::PaintChildren(gfx::Canvas* canvas) {
   if (inactive_tab_alpha < 255)
     canvas->Restore();
 
+#if defined(OS_WIN)

[sky, 2014/02/03 21:53:03]

I would rather move the ifdef to a function with a descriptive name. Maybe
something like ShouldFadeUnselectedTabs().

[Matt Giuca, 2014/02/05 23:25:31]

Done.

   if (GetWidget()->ShouldUseNativeFrame()) {
+    // On Windows, a native frame implies Glass.
     // Make sure non-active tabs are somewhat transparent.
     SkPaint paint;
     // If there are multiple tabs selected, fade non-selected tabs more to make
@@ -1346,6 +1355,7 @@ void TabStrip::PaintChildren(gfx::Canvas* canvas) {
     // The tabstrip area overlaps the toolbar area by 2 px.
     canvas->DrawRect(gfx::Rect(0, 0, width(), height() - 2), paint);
   }
+#endif
 
   // Now selected but not active. We don't want these dimmed if using native
   // frame, so they're painted after initial pass.