Add download button to MediaDocument on Android.

content/browser/android/content_startup_flags.cc

 // 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.
 
 #include "content/browser/android/content_startup_flags.h"
 
 #include "base/android/build_info.h"
 #include "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 24 matching lines @@
     // internal code checks this directly, but it wouldn't normally get set when
     // we are implementing an embedded WebView.
     parsed_command_line->AppendSwitch(switches::kSingleProcess);
   }
 
   parsed_command_line->AppendSwitch(cc::switches::kEnableBeginFrameScheduling);
 
   parsed_command_line->AppendSwitch(switches::kEnablePinch);
   parsed_command_line->AppendSwitch(switches::kEnableOverlayScrollbar);
   parsed_command_line->AppendSwitch(switches::kValidateInputEventStream);
+  parsed_command_line->AppendSwitch(
+      switches::kEnableMediaDocumentDownloadButton);
 
   if (base::android::BuildInfo::GetInstance()->sdk_int() >=
       base::android::SDK_VERSION_MARSHMALLOW) {
     parsed_command_line->AppendSwitch(switches::kEnableLongpressDragSelection);
     parsed_command_line->AppendSwitchASCII(
         switches::kTouchTextSelectionStrategy, "direction");
   }
 
   // There is no software fallback on Android, so don't limit GPU crashes.
   parsed_command_line->AppendSwitch(switches::kDisableGpuProcessCrashLimit);
@@ skipping 26 matching lines @@
   }
 
   cc::LayerSettings layer_settings;
   layer_settings.use_compositor_animation_timelines =
       !parsed_command_line->HasSwitch(
           switches::kDisableAndroidCompositorAnimationTimelines);
   Compositor::SetLayerSettings(layer_settings);
 }
 
 }  // namespace content