[Telemetry] Allow memory info to go missing on non-rooted devices.

BUG=400734

Review URL: https://codereview.chromium.org/440783003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287593 0039d316-1c4b-4281-b951-d872f2087c98

tools/telemetry/telemetry/core/browser.py

@@ -177,10 +177,12 @@ class Browser(object):
     """
     self._platform_backend.PurgeUnpinnedMemory()
     result = self._GetStatsCommon(self._platform_backend.GetMemoryStats)
-    result['SystemCommitCharge'] = \
-        self._platform_backend.GetSystemCommitCharge()
-    result['SystemTotalPhysicalMemory'] = \
-        self._platform_backend.GetSystemTotalPhysicalMemory()
+    commit_charge = self._platform_backend.GetSystemCommitCharge()
+    if commit_charge:
+      result['SystemCommitCharge'] = commit_charge
+    total = self._platform_backend.GetSystemTotalPhysicalMemory()
+    if total:
+      result['SystemTotalPhysicalMemory'] = total
     return result
 
   @property

tools/telemetry/telemetry/core/platform/proc_supporting_platform_backend.py

@@ -21,6 +21,8 @@ class ProcSupportingPlatformBackend(platform_backend.PlatformBackend):
   def GetSystemCommitCharge(self):
     meminfo_contents = self._GetFileContents('/proc/meminfo')
     meminfo = self._GetProcFileDict(meminfo_contents)
+    if not meminfo:
+      return None
     return (self._ConvertKbToByte(meminfo['MemTotal'])
             - self._ConvertKbToByte(meminfo['MemFree'])
             - self._ConvertKbToByte(meminfo['Buffers'])
@@ -30,6 +32,8 @@ class ProcSupportingPlatformBackend(platform_backend.PlatformBackend):
   def GetSystemTotalPhysicalMemory(self):
     meminfo_contents = self._GetFileContents('/proc/meminfo')
     meminfo = self._GetProcFileDict(meminfo_contents)
+    if not meminfo:
+      return None
     return self._ConvertKbToByte(meminfo['MemTotal'])
 
   def GetCpuStats(self, pid):