Make breakpad, gcl and presubmit_support dependencies optional

gclient_utils.py

Index: gclient_utils.py
diff --git a/gclient_utils.py b/gclient_utils.py
index 6ea091c12ce1624c2691a136bce0f06bf75a92ce..4944cf96744b4771402fd9c8ad33cbccbc879af5 100644
--- a/gclient_utils.py
+++ b/gclient_utils.py
@@ -35,15 +35,19 @@ class CheckCallError(OSError):
     self.stdout = stdout
 
 
-def CheckCall(command, cwd=None):
+def CheckCall(command, cwd=None, print_error=True):
   """Like subprocess.check_call() but returns stdout.
 
   Works on python 2.4
   """
   try:
+    stderr = None
+    if not print_error:
+      stderr = subprocess.PIPE
     process = subprocess.Popen(command, cwd=cwd,
                                shell=sys.platform.startswith('win'),
-                               stdout=subprocess.PIPE)
+                               stdout=subprocess.PIPE,
+                               stderr=stderr)
     output = process.communicate()[0]
   except OSError, e:
     raise CheckCallError(command, cwd, errno, None)