[Fuchsia] Implement FuchsiaVideoDecoder.

The new FuchsiaVideoDecoder implements VideoDecoder interface on top of
fuchsia.mediacodec API. It's currently not used anywhere yet.

Unittests added in this CL are  marked as MANUAL because we have only
have HW-based mediacodec implementation that doesn't work in qemu on bots.

Bug: 876519
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I59ebd716decef7940eb227a25967bad757bf3e82
Reviewed-on: https://chromium-review.googlesource.com/c/1287930
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603300}

build/config/fuchsia/testing_sandbox_policy

@@ -5,6 +5,7 @@
   "services": [
       "fuchsia.fonts.Provider",
       "fuchsia.media.Audio",
+      "fuchsia.mediacodec.CodecFactory",
       "fuchsia.net.LegacySocketProvider",
       "fuchsia.netstack.Netstack",
       "fuchsia.process.Launcher",

media/gpu/BUILD.gn

@@ -122,6 +122,7 @@ component("gpu") {
     "//gpu/command_buffer/common:gles2_utils",
     "//gpu/command_buffer/service:gles2",
     "//gpu/ipc/service",
+    "//third_party/libyuv",
     "//ui/base",
     "//ui/display/types",
     "//ui/gl",
@@ -202,7 +203,6 @@ component("gpu") {
       "//gpu/ipc/common:ipc_common_sources",
       "//media/mojo:buildflags",
       "//services/service_manager/public/cpp:cpp",
-      "//third_party/libyuv",
       "//ui/gl:gl_jni_headers",
     ]
 
@@ -214,16 +214,21 @@ component("gpu") {
     }
   }
 
+  if (is_fuchsia) {
+    sources += [
+      "fuchsia/fuchsia_video_decoder.cc",
+      "fuchsia/fuchsia_video_decoder.h",
+    ]
+    deps += [ "//third_party/fuchsia-sdk/sdk:mediacodec" ]
+  }
+
   if (use_v4lplugin) {
     sources += get_target_outputs(":libv4l2_generate_stubs")
     deps += [ ":libv4l2_generate_stubs" ]
   }
 
   if (use_v4l2_codec) {
-    deps += [
-      "//third_party/libyuv",
-      "//ui/ozone",
-    ]
+    deps += [ "//ui/ozone" ]
     sources += [
       "v4l2/generic_v4l2_device.cc",
       "v4l2/generic_v4l2_device.h",
@@ -288,7 +293,6 @@ component("gpu") {
     public_deps += [ "//media/base/win" ]
     deps += [
       "//third_party/angle:includes",
-      "//third_party/libyuv",
       "//ui/display",
     ]
     libs += [
@@ -635,6 +639,9 @@ source_set("unit_tests") {
   if (use_v4l2_codec || use_vaapi) {
     sources += [ "vp8_decoder_unittest.cc" ]
   }
+  if (is_fuchsia) {
+    sources += [ "fuchsia/fuchsia_video_decoder_unittest.cc" ]
+  }
   if (is_win && enable_library_cdms) {
     sources += [
       "windows/d3d11_cdm_proxy_unittest.cc",