Allow disabling warnings as errors in GN

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 4d3c6ba0c09093bd5137cd32c4d37cdee1db6d40..754663520eadc9ac10e1b5f52dceee3ca7463bae 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -22,6 +22,11 @@ if (is_win) {
 }
 
 declare_args() {
+  # Default to warnings as errors for default workflow, where we catch
+  # warnings with known toolchains. Allow overriding this e.g. for Chromium
+  # builds on Linux that could use a different version of the compiler.
+  treat_warnings_as_errors = true
+
   # Normally, Android builds are lightly optimized, even for debug builds, to
   # keep binary size down. Setting this flag to true disables such optimization
   android_full_debug = false
@@ -704,13 +709,16 @@ config("default_warnings") {
     cflags += [
       # Enables.
       "-Wendif-labels",  # Weird old-style text after an #endif.
-      "-Werror",  # Warnings as errors.
 
       # Disables.
       "-Wno-missing-field-initializers",  # "struct foo f = {0};"
       "-Wno-unused-parameter",  # Unused function parameters.
     ]
 
+    if (treat_warnings_as_errors) {
+      cflags += [ "-Werror" ]

[Dirk Pranke, 2015/11/06 17:56:54]

Does it make sense to make this work with the other toolchains as well?

If not, does it make sense to rename this as 'treat_warnings_as_errors_on_linux'
to be clearer?

I realize we probably only need and use this on linux today, so either solution
is fine as long as it's clear.

[brettw, 2015/11/09 02:25:02]

Yeah, it makes sense to put this check around the /WX switch in the Windows
section as well.

+    }
+
     if (is_mac) {
       cflags += [ "-Wnewline-eof" ]
       if (!is_nacl) {