GN: fixes for the official build.

The C++ define OFFICIAL_BUILD wasn't getting set, and the widevine version .rc files was getting linked twice.

CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:android_chromium_gn_compile_dbg,android_chromium_gn_compile_rel;tryserver.chromium.win:win8_chromium_gn_rel,win8_chromium_gn_dbg;tryserver.chromium.mac:mac_chromium_gn_rel,mac_chromium_gn_dbg

R=dpranke
TBR=ddorwin@chromium.org

Review URL: https://codereview.chromium.org/1134623003

Cr-Original-Commit-Position: refs/heads/master@{#329308}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 303920e6cd9d352e7a7b4e9bdcc2f28a30ac22fa

config/BUILD.gn

@@ -41,9 +41,8 @@ declare_args() {
 #
 # For now we define these globally to match the current GYP build.
 config("feature_flags") {
-  # TODO(brettw) most of these need to be parameterized.
+  # TODO(brettw) this probably needs to be parameterized.
   defines = [
-    "CHROMIUM_BUILD",
     "V8_DEPRECATION_WARNINGS",  # Don't use deprecated V8 APIs anywhere.
   ]
 
@@ -239,6 +238,14 @@ config("feature_flags") {
     defines += [ "MOBILE_SAFE_BROWSING" ]
     defines += [ "SAFE_BROWSING_SERVICE" ]
   }
+  if (is_official_build) {
+    defines += [ "OFFICIAL_BUILD" ]
+  }
+  if (is_chrome_branded) {
+    defines += [ "GOOGLE_CHROME_BUILD" ]
+  } else {
+    defines += [ "CHROMIUM_BUILD" ]
+  }
 }
 
 # Debug/release ----------------------------------------------------------------