Make gn.py support root directories other than 'src'.

gclient_utils.py

Index: gclient_utils.py
diff --git a/gclient_utils.py b/gclient_utils.py
index e8d916e78d5d2a8aeba4cbf61bebf7b64ad79084..a21e65a5fc31c5d01af67dc395f1ea65fabea86d 100644
--- a/gclient_utils.py
+++ b/gclient_utils.py
@@ -681,7 +681,10 @@ def GetBuildtoolsPath():
     if os.path.exists(os.path.join(top_dir, 'buildtools')):
       return os.path.join(top_dir, 'buildtools')
     return None
-  return os.path.join(gclient_root, 'src', 'buildtools')
+
+  # Some projects' top directory is not named 'src'.
+  source_dir_name = GetGClientPrimarySolutionName(gclient_root) or 'src'
+  return os.path.join(gclient_root, source_dir_name, 'buildtools')
 
 
 def GetBuildtoolsPlatformBinaryPath():
@@ -713,6 +716,17 @@ def GetExeSuffix():
   return ''
 
 
+def GetGClientPrimarySolutionName(gclient_root_dir_path):
+  """Returns the name of the primary solution in the .gclient file specified."""
+  gclient_config_file = os.path.join(gclient_root_dir_path, '.gclient')
+  env = {}
+  execfile(gclient_config_file, env)
+  solutions = env.get('solutions', [])
+  if solutions:
+    return solutions[0].get('name')
+  return None
+
+
 def GetGClientRootAndEntries(path=None):
   """Returns the gclient root and the dict of entries."""
   config_file = '.gclient_entries'