add app.setLocale() (#11469)

* infrastructure for setLocale via klang

* add documentation for setLocale

* add test for setLocale

* fix spec

* add spec and update docs

* fix carriage feeds on windows

* SetLocale() sets LC_ALL on Linux

* in SetLocale() on Linux, use g_setenv()

* fix tyop: '#ifdef OSX_POSIX'

* make the linter happy

* improvements from review

brightray/browser/browser_main_parts.h

@@ -6,6 +6,7 @@
 #define BRIGHTRAY_BROWSER_BROWSER_MAIN_PARTS_H_
 
 #include <memory>
+#include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
@@ -62,6 +63,7 @@ class BrowserMainParts : public content::BrowserMainParts {
 #endif
 
   std::unique_ptr<views::LayoutProvider> layout_provider_;
+  std::string custom_locale_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserMainParts);
 };