Remove OnThemeChanged and associated ViewMsg_ThemeChanged

ViewMsg_ThemeChanged was never sent, and even if it was, the only code
path that did anything was

#if USE_AURA
// nothing
#elif OS_WIN
// do stuff
...

so it was never going to run. Noticed while trying to clean up
NativeThemeWin usage from Blink, which also makes little-to-no sense and
causes the linked bug.

R=jam@chromium.org
BUG=258201

Review-Url: https://codereview.chromium.org/2287813002
Cr-Commit-Position: refs/heads/master@{#415371}

content/common/view_messages.h

@@ -660,9 +660,6 @@ IPC_MESSAGE_ROUTED2(ViewMsg_EnumerateDirectoryResponse,
 // Expects a ClosePage_ACK message when finished.
 IPC_MESSAGE_ROUTED0(ViewMsg_ClosePage)
 
-// Notifies the renderer about ui theme changes
-IPC_MESSAGE_ROUTED0(ViewMsg_ThemeChanged)
-
 // Notifies the renderer that a paint is to be generated for the rectangle
 // passed in.
 IPC_MESSAGE_ROUTED1(ViewMsg_Repaint,

content/renderer/render_view_impl.cc

@@ -182,12 +182,6 @@
 #include "content/renderer/android/phone_number_detector.h"
 #include "ui/gfx/geometry/rect_f.h"
 
-#elif defined(OS_WIN)
-// TODO(port): these files are currently Windows only because they concern:
-//   * theming
-#include "ui/native_theme/native_theme_win.h"
-#elif defined(USE_X11)
-#include "ui/native_theme/native_theme.h"
 #elif defined(OS_MACOSX)
 #include "skia/ext/skia_utils_mac.h"
 #endif
@@ -1331,7 +1325,6 @@ bool RenderViewImpl::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(ViewMsg_EnumerateDirectoryResponse,
                         OnEnumerateDirectoryResponse)
     IPC_MESSAGE_HANDLER(ViewMsg_ClosePage, OnClosePage)
-    IPC_MESSAGE_HANDLER(ViewMsg_ThemeChanged, OnThemeChanged)
     IPC_MESSAGE_HANDLER(ViewMsg_MoveOrResizeStarted, OnMoveOrResizeStarted)
     IPC_MESSAGE_HANDLER(ViewMsg_ClearFocusedElement, OnClearFocusedElement)
     IPC_MESSAGE_HANDLER(ViewMsg_SetBackgroundOpaque, OnSetBackgroundOpaque)
@@ -2515,19 +2508,6 @@ void RenderViewImpl::OnClose() {
   RenderWidget::OnClose();
 }
 
-void RenderViewImpl::OnThemeChanged() {
-#if defined(USE_AURA)
-  // Aura doesn't care if we switch themes.
-#elif defined(OS_WIN)
-  ui::NativeThemeWin::instance()->CloseHandles();
-  if (webview())
-    webview()->themeChanged();
-#else  // defined(OS_WIN)
-  // TODO(port): we don't support theming on non-Windows platforms yet
-  NOTIMPLEMENTED();
-#endif
-}
-
 void RenderViewImpl::OnMoveOrResizeStarted() {
   if (webview())
     webview()->hidePopups();

content/renderer/render_view_impl.h

@@ -625,7 +625,6 @@ class CONTENT_EXPORT RenderViewImpl
   void OnSetWebUIProperty(const std::string& name, const std::string& value);
   void OnSetZoomLevelForLoadingURL(const GURL& url, double zoom_level);
   void OnSuppressDialogsUntilSwapOut();
-  void OnThemeChanged();
   void OnUpdateTargetURLAck();
   void OnUpdateWebPreferences(const WebPreferences& prefs);
   void OnSetPageScale(float page_scale_factor);