Make page_cycler.py fully measure memory for each page.

tools/telemetry/telemetry/core/platform/android_platform_backend.py

Index: tools/telemetry/telemetry/core/platform/android_platform_backend.py
diff --git a/tools/telemetry/telemetry/core/platform/android_platform_backend.py b/tools/telemetry/telemetry/core/platform/android_platform_backend.py
index 2332d015f3b8701913749358eb797da9824c3df3..112115c8774ebf201d088c9ba9b38ebf555eabad 100644
--- a/tools/telemetry/telemetry/core/platform/android_platform_backend.py
+++ b/tools/telemetry/telemetry/core/platform/android_platform_backend.py
@@ -8,6 +8,7 @@ from telemetry.core import exceptions
 from telemetry.core import platform
 from telemetry.core import util
 from telemetry.core.platform import proc_supporting_platform_backend
+from telemetry.core.platform.profiler import android_prebuilt_profiler_helper
 
 # Get build/android scripts into our path.
 util.AddDirToPythonPath(util.GetChromiumSrcDir(), 'build', 'android')
@@ -102,8 +103,19 @@ class AndroidPlatformBackend(
       return {}
     return super(AndroidPlatformBackend, self).GetCpuTimestamp()
 
+  def PurgeUnpinnedMemory(self):
+    """Purges the unpinned ashmem memory for the whole system.
+
+    This can be used to make memory measurements more stable in particular.
+    """
+    android_prebuilt_profiler_helper.InstallOnDevice(self._adb, 'purge_ashmem')
+    if self._adb.RunShellCommand(
+        android_prebuilt_profiler_helper.GetDevicePath('purge_ashmem'),
+        log_result=True):
+      return
+    raise Exception('Error while purging ashmem.')
+
   def GetMemoryStats(self, pid):
-    self._adb.PurgeUnpinnedAshmem()
     memory_usage = self._adb.GetMemoryUsageForPid(pid)[0]
     return {'ProportionalSetSize': memory_usage['Pss'] * 1024,
             'SharedDirty': memory_usage['Shared_Dirty'] * 1024,