get webframe_impl.cc to compile on linux

base/gfx/bitmap_platform_device_linux.cc

Index: base/gfx/bitmap_platform_device_linux.cc
diff --git a/base/gfx/bitmap_platform_device_linux.cc b/base/gfx/bitmap_platform_device_linux.cc
index 1211a1536d5bb74004c73748f7e3bdffc5c8bb8a..171f6b9853c0d93f8a4ceedc84623f92c479633a 100644
--- a/base/gfx/bitmap_platform_device_linux.cc
+++ b/base/gfx/bitmap_platform_device_linux.cc
@@ -38,6 +38,12 @@ BitmapPlatformDeviceLinux::BitmapPlatformDeviceLinux(const SkBitmap& bitmap)
     : PlatformDeviceLinux(bitmap) {
 }
 
+BitmapPlatformDeviceLinux::BitmapPlatformDeviceLinux(
+    const BitmapPlatformDeviceLinux& other)
+    : PlatformDeviceLinux(const_cast<BitmapPlatformDeviceLinux&>(
+                          other).accessBitmap(true)) {
+}
+
 BitmapPlatformDeviceLinux::~BitmapPlatformDeviceLinux() {
 }