media/gpu: Separate command_buffer_helper to new build target.

Originally command_buffer_helper is at //media/gpu target.
At the next CL, //media/gpu/linux will use command_buffer_helper.
But //media/gpu already depends on //media/gpu/linux.
To avoid circular dependency, we separate command_buffer_helper to a
isolated build target.

BUG=941330
TEST=Build chrome for chromeos and linux target

Change-Id: Ia456b36b1a7229aa58ccaba4248c29d17ca698ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1564364
Auto-Submit: Chih-Yu Huang <akahuang@chromium.org>
Commit-Queue: Chih-Yu Huang <akahuang@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: David Staessens <dstaessens@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664675}

media/gpu/BUILD.gn

@@ -50,10 +50,6 @@ component("gpu") {
   defines = [ "MEDIA_GPU_IMPLEMENTATION" ]
 
   sources = [
-    "command_buffer_helper.cc",
-    "command_buffer_helper.h",
-    "gles2_decoder_helper.cc",
-    "gles2_decoder_helper.h",
     "gpu_video_accelerator_util.cc",
     "gpu_video_accelerator_util.h",
     "gpu_video_decode_accelerator_factory.cc",
@@ -64,6 +60,7 @@ component("gpu") {
 
   public_deps = [
     ":buildflags",
+    ":command_buffer_helper",
     ":common",
     ":image_processor",
     ":video_frame_mapper",
@@ -74,9 +71,6 @@ component("gpu") {
     "//ui/gfx/geometry",
   ]
   deps = [
-    "//gpu/command_buffer/common:gles2_utils",
-    "//gpu/command_buffer/service:gles2",
-    "//gpu/ipc/service",
     "//third_party/libyuv",
     "//ui/base",
     "//ui/display/types",
@@ -285,6 +279,26 @@ source_set("common") {
   ]
 }
 
+source_set("command_buffer_helper") {
+  defines = [ "MEDIA_GPU_IMPLEMENTATION" ]
+  sources = [
+    "command_buffer_helper.cc",
+    "command_buffer_helper.h",
+    "gles2_decoder_helper.cc",
+    "gles2_decoder_helper.h",
+  ]
+
+  public_deps = [
+    "//base",
+    "//gpu/command_buffer/common",
+    "//gpu/command_buffer/common:gles2_utils",
+    "//gpu/command_buffer/service",
+    "//gpu/command_buffer/service:gles2",
+    "//gpu/ipc/service",
+    "//ui/gl",
+  ]
+}
+
 source_set("image_processor") {
   defines = [ "MEDIA_GPU_IMPLEMENTATION" ]
   sources = [
@@ -518,10 +532,8 @@ static_library("test_support") {
     "test/fake_command_buffer_helper.h",
   ]
   configs += [ "//media:media_config" ]
-  deps = [
-    ":gpu",
-  ]
   public_deps = [
+    ":gpu",
     "//base",
     "//media",
   ]