[Telemetry] Refactoring in preparation for video-based Speed Index support.

tools/telemetry/telemetry/core/platform/__init__.py

Index: tools/telemetry/telemetry/core/platform/__init__.py
diff --git a/tools/telemetry/telemetry/core/platform/__init__.py b/tools/telemetry/telemetry/core/platform/__init__.py
index ad5909ce77f453b1f10f63ad35ea04bcc5a6810e..a613de43fda35c075965e8967b467095bbb52314 100644
--- a/tools/telemetry/telemetry/core/platform/__init__.py
+++ b/tools/telemetry/telemetry/core/platform/__init__.py
@@ -128,6 +128,33 @@ class Platform(object):
     """Installs the given application."""
     return self._platform_backend.InstallApplication(application)
 
+  def CanCaptureBrowserVideo(self):
+    """Returns a bool indicating whether the platform supports video capture
+    of the browser's content.
+    """
+    return self._platform_backend.CanCaptureBrowserVideo()
+
+  def StartBrowserVideoCapture(self, tab, max_bitrate_mbps):
+    """Starts recording video of the browser's content.
+
+    Outer framing by the OS and browser window is not included.
+
+    Args:
+      tab: The tab for which to capture.
+      max_bitrate_mbps: The maximum bitrate in MegaBits Per Second to capture.
+          There is no guarantee the platform can actually deliver the requested
+          rate. Must be in range [0.1, 100].

[szym, 2013/11/29 11:05:12]

Should webcam capture enforce the bitrate limit as well?

[tonyg, 2013/11/29 20:42:07]

To your point, max_bitrate seems like it requires implementation-specific
knowledge. I've changed it to min_bitrate instead. Because that's what a user of
this api requires. The platform will be responsible for achieving that bitrate
or throwing an exception. That seems to work better for webcam, right?

+    """
+    return self._platform_backend.StartBrowserVideoCapture(
+        tab, max_bitrate_mbps)
+
+  def StopBrowserVideoCapture(self):

[tonyg, 2013/11/29 20:42:07]

I changed this to return keyframes instead of all frames. If avconv can
efficiently ignore duplicate frames, it should make the memory and speed of this
API much more tenable.

+    """Stops recording browser content video.
+
+    Returns a list of bitmaps representing each video frame.
+    """
+    return self._platform_backend.StopBrowserVideoCapture()
+
 
 def CreatePlatformBackendForCurrentOS():
   if sys.platform.startswith('linux'):