GN: Create a :gles2_interface target to resolve some check errors in //cc.

gles2_interface.h defines a pure virtual interface; targets which use it should
depend on it, but not necessarily on an implementation target. Consequently,
a //gpu/command_buffer/client:gles2_interface target was created to reflect the
dependency on this interface without linking a particular implementation.

This resolves an issue with //cc trying to use this header without having a
dependency on a target which includes it.

Review URL: https://codereview.chromium.org/464153002

Cr-Commit-Position: refs/heads/master@{#294956}

cc/BUILD.gn

@@ -478,6 +478,7 @@ component("cc") {
     "//base",
     "//base/third_party/dynamic_annotations",
     "//gpu",
+    "//gpu/command_buffer/client:gles2_interface",
     "//media",
     "//skia",
     "//ui/events:events_base",
@@ -642,6 +643,10 @@ source_set("test_support") {
   if (!is_android) {  # TODO(GYP) Enable on Android when osmesa links.
     deps += [ "//third_party/mesa:osmesa" ]
   }
+
+  forward_dependent_configs_from = [
+    "//gpu:test_support",
+  ]
 }
 
 test("cc_unittests") {
@@ -775,6 +780,7 @@ test("cc_unittests") {
     "//cc/surfaces",
     "//gpu",
     "//gpu:test_support",
+    "//gpu/command_buffer/client:gles2_interface",
     "//gpu/command_buffer/common:gles2_utils",
     "//media",
     "//testing/gmock",

content/common/BUILD.gn

@@ -28,6 +28,7 @@ source_set("common") {
     "//base",
     "//build/util:webkit_version",
     "//components/tracing",
+    "//gpu/command_buffer/client:gles2_interface",
     "//gpu/command_buffer/common",
     "//net",
     "//skia",

content/renderer/BUILD.gn

@@ -32,6 +32,7 @@ source_set("renderer") {
     "//content/public/common:common_sources",
     "//gin",
     "//gpu",
+    "//gpu/command_buffer/client:gles2_interface",
     "//jingle:jingle_glue",
     "//media",
     "//media/blink",

gpu/BUILD.gn

@@ -56,14 +56,16 @@ source_set("test_support") {
     "command_buffer/client/gles2_interface_stub.h",
   ]
 
-  configs += [ "//third_party/khronos:khronos_headers" ]
-
   deps = [
     ":gpu",
+    "//gpu/command_buffer/client:gles2_interface",
     "//testing/gmock",
     "//testing/gtest",
     "//ui/gl:gl_unittest_utils",
   ]
+  forward_dependent_configs_from = [
+    "//gpu/command_buffer/client:gles2_interface",
+  ]
 }
 
 test("gl_tests") {

gpu/command_buffer/client/BUILD.gn

@@ -77,7 +77,6 @@ gles2_implementation_source_files = [
   "gles2_implementation.cc",
   "gles2_implementation.h",
   "gles2_implementation_impl_autogen.h",
-  "gles2_interface.h",
   "gles2_trace_implementation_autogen.h",
   "gles2_trace_implementation.cc",
   "gles2_trace_implementation.h",
@@ -95,6 +94,17 @@ gles2_implementation_source_files = [
   "vertex_array_object_manager.h",
 ]
 
+# Provides GLES2 interface, but does not cause any implementation to be linked
+# in. Useful when a target uses the interface, but permits its users to choose
+# an implementation.
+source_set("gles2_interface") {
+  sources = [ "gles2_interface.h" ]
+  direct_dependent_configs = [ "//third_party/khronos:khronos_headers" ]
+  deps = [
+    "//base",
+  ]
+}
+
 # Library emulates GLES2 using command_buffers.
 component("gles2_implementation") {
   sources = gles2_implementation_source_files
@@ -109,6 +119,7 @@ component("gles2_implementation") {
 
   deps = [
     ":gles2_cmd_helper",
+    ":gles2_interface",
     "//base",
     "//gpu/command_buffer/common",
     "//ui/gfx/geometry",
@@ -133,6 +144,7 @@ component("gles2_implementation_client_side_arrays") {
 
   deps = [
     ":gles2_cmd_helper",
+    ":gles2_interface",
     "//base",
     "//gpu/command_buffer/common",
     "//ui/gfx/geometry",
@@ -171,6 +183,7 @@ component("gles2_c_lib") {
 
   deps = [
     ":client",
+    ":gles2_interface",
     "//base",
     "//base/third_party/dynamic_annotations",
     "//gpu/command_buffer/common",

mojo/examples/sample_app/BUILD.gn

@@ -16,6 +16,7 @@ shared_library("sample_app") {
 
   deps = [
     ":spinning_cube",
+    "//gpu/command_buffer/client:gles2_interface",
     "//mojo/public/cpp/application:standalone",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/utility",

mojo/gles2/BUILD.gn

@@ -23,6 +23,7 @@ component("gles2") {
     "//gpu/command_buffer/client",
     "//gpu/command_buffer/common",
     "//gpu/command_buffer/client:gles2_implementation",
+    "//gpu/command_buffer/client:gles2_interface",
     "//mojo/services/gles2:bindings",
     "//mojo/services/gles2:interfaces",
     "//mojo/environment:chromium",

ui/aura/BUILD.gn

@@ -253,6 +253,7 @@ executable("bench") {
     "//base",
     "//base:i18n",
     "//cc",
+    "//gpu/command_buffer/client:gles2_interface",
     "//skia",
     "//third_party/icu",
     "//ui/base",