Revert "chromecast: force disable new accelerated video decoder"

This reverts commit 0fc9ef09.

Reason for revert: This no longer compiles, the flag is removed from
our build after 0f1575a6 ("media/chromeos: refactor flags enabling new VideoDecoder"). Probably it's no longer needed.

Original change's description:
> chromecast: force disable new accelerated video decoder
> 
> The new accelerated video decoder uses V4L2SliceVDA, which is
> not supported by Cast devices.
> 
> So instead, we will force disable use of this new decoder
> through command line switch, which will fallback to use
> VdaVideoDecoder, which uses V4L2VDA.
> 
> Bug: b/158230739
> Test: Verify mirroring on Cast display devices
> Change-Id: I7765e6861c09a0357e2d923a20c9a56c1bdcb065
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2238876
> Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
> Reviewed-by: Sean Topping <seantopping@chromium.org>
> Reviewed-by: Luke Halliwell (slow) <halliwell@chromium.org>
> Reviewed-by: Yuchen Liu <yucliu@chromium.org>
> Commit-Queue: Peter Qiu <zqiu@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#776861}

TBR=zqiu@chromium.org,halliwell@chromium.org,tguilbert@chromium.org,seantopping@chromium.org,yucliu@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: b/158230739
Change-Id: Idaac0f78fc54b6fb4bf0d2f028ad5be96cfd7ebd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2306377Reviewed-by: Michael Spang <spang@chromium.org>
Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Commit-Queue: Yuchen Liu <yucliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790123}

chromecast/browser/DEPS

@@ -49,7 +49,6 @@ include_rules = [
   "+extensions/shell/browser/api",
   "+gin/v8_initializer.h",
   "+gpu/command_buffer/service/gpu_switches.h",
-  "+media",
   "+media/audio",
   "+media/base",
   "+media/mojo",

chromecast/browser/cast_browser_main_parts.cc

@@ -69,7 +69,6 @@
 #include "gpu/command_buffer/service/gpu_switches.h"
 #include "media/base/media.h"
 #include "media/base/media_switches.h"
-#include "media/media_buildflags.h"
 #include "net/base/network_change_notifier.h"
 #include "services/network/public/cpp/shared_url_loader_factory.h"
 #include "ui/base/ui_base_switches.h"
@@ -329,11 +328,6 @@ const DefaultCommandLineSwitch kDefaultSwitches[] = {
 #endif
 #endif
 #endif  // defined(OS_LINUX)
-#if BUILDFLAG(USE_CHROMEOS_MEDIA_ACCELERATION)
-    // Force disable new video decoder, since it uses slice H.264, which is
-    // not currently supported on Linux-based Cast devices.
-    {switches::kForceDisableNewAcceleratedVideoDecoder, ""},
-#endif  // BUILDFLAG(USE_CHROMEOS_MEDIA_ACCELERATION)
     // It's better to start GPU process on demand. For example, for TV platforms
     // cast starts in background and can't render until TV switches to cast
     // input.