Add perf tests for starting Chrome with URL

tools/telemetry/telemetry/page/page_test.py

Index: tools/telemetry/telemetry/page/page_test.py
diff --git a/tools/telemetry/telemetry/page/page_test.py b/tools/telemetry/telemetry/page/page_test.py
index 368aa894706c1fb48d66ebe8a54bbd8ada56cebc..1896292e2fb770ec6f77b97807bef0ab8e6d8ab0 100644
--- a/tools/telemetry/telemetry/page/page_test.py
+++ b/tools/telemetry/telemetry/page/page_test.py
@@ -107,10 +107,19 @@ class PageTest(object):
   def close_tabs_before_run(self, close_tabs):
     self._close_tabs_before_run = close_tabs
 
-  def NeedsBrowserRestartAfterEachRun(self, browser):  # pylint: disable=W0613
-    """Override to specify browser restart after each run."""
+  def AlwaysRestartBrowserForEachRun(self):
+    """ Should be browser be restarted after each run - browser independent.

[jeremy, 2013/12/15 13:03:36]

nit: "Should the..."

And if this returns false that means that the browser gets restarted after the
whole pageset?

[aberent, 2013/12/16 17:07:43]

Done.

+
+    Can be called at any time."""
     return self._needs_browser_restart_after_each_run
 
+  def NeedsBrowserRestartAfterEachRun(self, browser):  # pylint: disable=W0613
+    """Browser dependent version of AlwaysRestartBrowserForEachRun.
+
+    Can only be called once the browser has stared. Override this if the test
+    has to restart the browser for some browsers but not all."""

[jeremy, 2013/12/15 13:03:36]

Not clear what "browser dependent" means in this context :( Can you please
expand/rephrase the comment?

esp. the difference between this and the previous function.

[aberent, 2013/12/16 17:07:43]

I have renamed this to more accurately reflect what it does, and extended the
comments. The reason for this function is that image_decoding.py needs to call a
browser function to decide whether to restart the browser. 

+    return self.AlwaysRestartBrowserForEachRun()
+
   def AddCommandLineOptions(self, parser):
     """Override to expose command-line options for this test.