Added Tab.SnapshotContent and MapsGL example to telemetry

tools/telemetry/telemetry/tab.py

Index: tools/telemetry/telemetry/tab.py
diff --git a/tools/telemetry/telemetry/tab.py b/tools/telemetry/telemetry/tab.py
index 527a2e00fb94aea172a4d30a64c7a9106a2856e4..1e3825708e17243817da2742f284571dcee8f1ba 100644
--- a/tools/telemetry/telemetry/tab.py
+++ b/tools/telemetry/telemetry/tab.py
@@ -5,6 +5,7 @@ from telemetry import inspector_console
 from telemetry import inspector_page
 from telemetry import inspector_runtime
 from telemetry import util
+from telemetry import snapshot
 
 DEFAULT_TAB_TIMEOUT = 60
 
@@ -75,3 +76,23 @@ class Tab(object):
       rs = self._runtime.Evaluate('document.readyState')
       return rs == 'complete' or rs == 'interactive'
     util.WaitFor(IsReadyStateInteractiveOrBetter, timeout)
+

[nduca, 2012/11/09 21:19:00]

This should be a feature on inspector_page.py --- the likely path for this in
the future is page.screenshot. So, call it screnshot and put it on
inspector_page.

+  def SnapshotContent(self, timeout=DEFAULT_TAB_TIMEOUT):

[nduca, 2012/11/09 21:19:00]

So, what if someone calls this and the gpuBenchmarking extension isn't enabled?

if gpubenchmarkingextnesion not in this.browser.browserOptions:
  raise Exception("Browser was not started with --enable-blahblah")

[nduca, 2012/11/09 21:19:00]

"content"? That would imply we're taking a picture of the invisible parts too.
Screenshot might be good. Or whatever the word is that the inspector bug about
this says.

+    self._runtime.Evaluate("""

[nduca, 2012/11/09 21:19:00]

This function should have """Help text""" that explains what it does and what it
returns.

+        window.chrome.gpuBenchmarking.snapshotComplete = false;
+        window.chrome.gpuBenchmarking.windowSnapshot(function(snapshot) {
+            window.chrome.gpuBenchmarking.snapshotData = snapshot;
+            window.chrome.gpuBenchmarking.snapshotComplete = true;
+        });
+    """)
+
+    def IsSnapshotComplete():
+      return self._runtime.Evaluate(
+          'window.chrome.gpuBenchmarking.snapshotComplete')
+
+    util.WaitFor(IsSnapshotComplete, timeout)
+
+    snap = self._runtime.Evaluate('window.chrome.gpuBenchmarking.snapshotData')
+    if snap:
+      return snapshot.Snapshot(snap['data'])
+    return None