Add CommandLineArgumentParameter and use it for WebView tests

build/android/pylib/flag_changer.py

Index: build/android/pylib/flag_changer.py
diff --git a/build/android/pylib/flag_changer.py b/build/android/pylib/flag_changer.py
index 2cf5ae2fa16d62dd5643ef793482ec1281a1aa3b..c881bdae40af6747bd506d559925b17aacac3473 100644
--- a/build/android/pylib/flag_changer.py
+++ b/build/android/pylib/flag_changer.py
@@ -42,14 +42,7 @@ class FlagChanger(object):
     Args:
       flags: A list of flags to add on, eg. ['--single-process'].
     """
-    if flags:
-      assert flags[0] != 'chrome'
-
-    new_flags = self._state_stack[-1].copy()
-    for flag in flags:
-      new_flags.add(flag)
-    self._state_stack.append(new_flags)
-    self._UpdateCommandLineFile()
+    self.PushFlags(add=flags)
 
   def RemoveFlags(self, flags):
     """Removes flags from the command line, if they exist.
@@ -65,12 +58,29 @@ class FlagChanger(object):
              a switch with a value, you must use the exact string used to add
              it in the first place.
     """
-    if flags:
-      assert flags[0] != 'chrome'
+    self.PushFlags(remove=flags)
 
+  def PushFlags(self, add=None, remove=None):
+    """Appends and removes flags to/from the command line if they aren't already
+       there. Saves the current flags state on the stack, so a call to Restore
+       will change the state back to the one preceeding the call to PushFlags.
+
+    Args:
+      add: A list of flags to add on, eg. ['--single-process'].
+      remove: A list of flags to remove, eg. ['--single-process'].  Note that we
+              expect a complete match when removing flags; if you want to remove
+              a switch with a value, you must use the exact string used to add
+              it in the first place.
+    """
     new_flags = self._state_stack[-1].copy()
-    for flag in flags:
-      new_flags.discard(flag)
+    if add:
+      assert add[0] != 'chrome'
+      for flag in add:
+        new_flags.add(flag)
+    if remove:
+      assert remove[0] != 'chrome'
+      for flag in remove:
+        new_flags.discard(flag)
     self._state_stack.append(new_flags)
     self._UpdateCommandLineFile()