don't put a dropmarker in comboboxes if nsITheme says not to. b=370282 r/sr=roc

gfx/public/nsITheme.h

@@ -151,6 +151,11 @@ public:
   virtual PRBool ThemeDrawsFocusForWidget(nsPresContext* aPresContext,
                                           nsIFrame* aFrame,
                                           PRUint8 aWidgetType)=0;
+  
+  /**
+    * Should we insert a dropmarker inside of combobox button?
+   */
+  virtual PRBool ThemeNeedsComboboxDropmarker()=0;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsITheme, NS_ITHEME_IID)

layout/forms/nsComboboxControlFrame.cpp

@@ -653,15 +653,21 @@ nsComboboxControlFrame::Reflow(nsPresContext*          aPresContext,
 
   // Get the width of the vertical scrollbar.  That will be the width of the
   // dropdown button.
-  nsIScrollableFrame* scrollable;
-  CallQueryInterface(mListControlFrame, &scrollable);
-  NS_ASSERTION(scrollable, "List must be a scrollable frame");
-  nsBoxLayoutState bls(PresContext(), aReflowState.rendContext);
-  nscoord buttonWidth = scrollable->GetDesiredScrollbarSizes(&bls).LeftRight();
-
-  if (buttonWidth > aReflowState.ComputedWidth()) {
+  nscoord buttonWidth;
+  const nsStyleDisplay *disp = GetStyleDisplay();
+  if (IsThemed(disp) && !aPresContext->GetTheme()->ThemeNeedsComboboxDropmarker()) {
     buttonWidth = 0;
   }
+  else {
+    nsIScrollableFrame* scrollable;
+    CallQueryInterface(mListControlFrame, &scrollable);
+    NS_ASSERTION(scrollable, "List must be a scrollable frame");
+    nsBoxLayoutState bls(PresContext(), aReflowState.rendContext);
+    buttonWidth = scrollable->GetDesiredScrollbarSizes(&bls).LeftRight();
+    if (buttonWidth > aReflowState.ComputedWidth()) {
+      buttonWidth = 0;
+    }
+  }
 
   mDisplayWidth = aReflowState.ComputedWidth() - buttonWidth;
 

widget/src/cocoa/nsNativeThemeCocoa.h

@@ -84,6 +84,7 @@ public:
   PRBool ThemeSupportsWidget(nsPresContext* aPresContext, nsIFrame* aFrame, PRUint8 aWidgetType);
   PRBool WidgetIsContainer(PRUint8 aWidgetType);
   PRBool ThemeDrawsFocusForWidget(nsPresContext* aPresContext, nsIFrame* aFrame, PRUint8 aWidgetType);
+  PRBool ThemeNeedsComboboxDropmarker();
 
 protected:
 

widget/src/cocoa/nsNativeThemeCocoa.mm

@@ -1393,3 +1393,9 @@ nsNativeThemeCocoa::ThemeDrawsFocusForWidget(nsPresContext* aPresContext, nsIFra
   
   return PR_FALSE;
 }
+
+PRBool
+nsNativeThemeCocoa::ThemeNeedsComboboxDropmarker()
+{
+  return PR_FALSE;
+}

widget/src/gtk2/nsNativeThemeGTK.cpp

@@ -1072,3 +1072,9 @@ nsNativeThemeGTK::ThemeDrawsFocusForWidget(nsPresContext* aPresContext, nsIFrame
 {
   return PR_FALSE;
 }
+
+PRBool
+nsNativeThemeGTK::ThemeNeedsComboboxDropmarker()
+{
+  return PR_TRUE;
+}

widget/src/gtk2/nsNativeThemeGTK.h

@@ -90,6 +90,8 @@ public:
   NS_IMETHOD_(PRBool) ThemeDrawsFocusForWidget(nsPresContext* aPresContext,
                                                nsIFrame* aFrame, PRUint8 aWidgetType);
 
+  PRBool ThemeNeedsComboboxDropmarker();
+
   nsNativeThemeGTK();
   virtual ~nsNativeThemeGTK();
 

widget/src/windows/nsNativeThemeWin.cpp

@@ -1289,6 +1289,12 @@ nsNativeThemeWin::ThemeDrawsFocusForWidget(nsPresContext* aPresContext, nsIFrame
   return PR_FALSE;
 }
 
+PRBool
+nsNativeThemeWin::ThemeNeedsComboboxDropmarker()
+{
+  return PR_TRUE;
+}
+
 /* Windows 9x/NT/2000/Classic XP Theme Support */
 
 PRBool 

widget/src/windows/nsNativeThemeWin.h

@@ -83,6 +83,8 @@ public:
 
   PRBool ThemeDrawsFocusForWidget(nsPresContext* aPresContext, nsIFrame* aFrame, PRUint8 aWidgetType);
 
+  PRBool ThemeNeedsComboboxDropmarker();
+
   nsNativeThemeWin();
   virtual ~nsNativeThemeWin();