Sync defines with the GYP build.

build/config/BUILD.gn

Index: build/config/BUILD.gn
diff --git a/build/config/BUILD.gn b/build/config/BUILD.gn
index 2427b72afd920cf6b85a48d83f42a19fe5184bd4..5cf18403e948e8e55c93144f62659a5d5e6ac163 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -239,6 +239,9 @@ config("feature_flags") {
     defines += [ "MOBILE_SAFE_BROWSING" ]
     defines += [ "SAFE_BROWSING_SERVICE" ]
   }
+  if (is_official_build) {
+    defines += [ "OFFICIAL_BUILD" ]

[Dirk Pranke, 2015/05/12 00:09:41]

Didn't you have this in a different CL somewhere?

+  }
 }
 
 # Debug/release ----------------------------------------------------------------
@@ -271,6 +274,18 @@ config("debug") {
 
 config("release") {
   defines = [ "NDEBUG" ]
+
+  # Sanitizers.
+  # TODO(GYP) The GYP build has "release_valgrind_build == 0" for this
+  # condition. When Valgrind is set up, we need to do the same here.
+  if (!is_tsan) {
+    defines += [ "NVALGRIND" ]
+    if (!is_nacl) {
+      # NaCl always enables dynamic annotations. Currently this value is set to
+      # 1 for all .nexes.
+      defines += [ "DYNAMIC_ANNOTATIONS_ENABLED=0" ]

[Dirk Pranke, 2015/05/12 00:09:40]

I don't quite understand this comment; how is the second sentence different than
the first sentence? It's also a little weird that you're talking about what NaCl
does in the (!nacl) case. 

+    }
+  }
 }
 
 # Default libraries ------------------------------------------------------------