Refactor the PlatformContext layer to have only one class.

chrome/browser/views/theme_helpers.cc

Index: chrome/browser/views/theme_helpers.cc
diff --git a/chrome/browser/views/theme_helpers.cc b/chrome/browser/views/theme_helpers.cc
index 7d4375d053619b81e83dd9788968d221cc1b6465..1d63ea654adf98b218fe6060c514af930172ef5a 100644
--- a/chrome/browser/views/theme_helpers.cc
+++ b/chrome/browser/views/theme_helpers.cc
@@ -64,8 +64,8 @@ void GetRebarGradientColors(int width, int x1, int x2,
   // Extract the color values from the selected pixels
   // The | in the following operations forces the alpha to 0xFF. This is
   // needed as windows sets the alpha to 0 when it renders.
-  skia::BitmapPlatformDeviceWin& device =
-      static_cast<skia::BitmapPlatformDeviceWin&>(
+  skia::BitmapPlatformDevice& device =
+      static_cast<skia::BitmapPlatformDevice&>(
           canvas.getTopPlatformDevice());
   *c1 = 0xFF000000 | device.getColorAt(x1, 0);
   *c2 = 0xFF000000 | device.getColorAt(x2, 0);