Remove unused canvas_linux.cc and associated code.

ui/ui.gyp

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'includes': [
     'ui_resources.gypi',
@@ skipping 321 matching lines @@
         'base/x/x11_util_internal.h',
         'gfx/android/gfx_jni_registrar.cc',
         'gfx/android/gfx_jni_registrar.h',
         'gfx/android/java_bitmap.cc',
         'gfx/android/java_bitmap.h',
         'gfx/blit.cc',
         'gfx/blit.h',
         'gfx/canvas.cc',
         'gfx/canvas.h',
         'gfx/canvas_android.cc',
-        'gfx/canvas_linux.cc',
         'gfx/canvas_mac.mm',
         'gfx/canvas_paint.h',
         'gfx/canvas_paint_win.cc',
         'gfx/canvas_skia.cc',
         'gfx/canvas_skia_paint.h',
         'gfx/codec/jpeg_codec.cc',
         'gfx/codec/jpeg_codec.h',
         'gfx/codec/png_codec.cc',
         'gfx/codec/png_codec.h',
         'gfx/color_analysis.cc',
@@ skipping 127 matching lines @@
         ['OS!="ios"', {
           'dependencies': [
             '<(libjpeg_gyp_path):libjpeg',
           ],
         }],
         # TODO(asvitkine): Switch all platforms to use canvas_skia.cc.
         #                  http://crbug.com/105550
         ['use_canvas_skia==1', {
           'sources!': [
             'gfx/canvas_android.cc',
-            'gfx/canvas_linux.cc',
             'gfx/canvas_mac.mm',
           ],
         }, {  # use_canvas_skia!=1
           'sources!': [
             'gfx/canvas_skia.cc',
           ],
         }],
         ['use_aura==1', {
           'sources/': [
             ['exclude', 'gfx/gtk_'],
@@ skipping 274 matching lines @@
   ],
   'conditions': [
     ['inside_chromium_build == 1 and OS != "ios"', {
       # TODO(ios): The ui tests do not compile yet on iOS.
       'includes': [
         'ui_unittests.gypi',
       ]},
     ],
   ],
 }