Telemetry: adds CPU frequency stats.

tools/telemetry/telemetry/core/browser.py

Index: tools/telemetry/telemetry/core/browser.py
diff --git a/tools/telemetry/telemetry/core/browser.py b/tools/telemetry/telemetry/core/browser.py
index 39a18cfb30001a042e7df8c2400b1d677e9f75cd..ff015365045c009fadbd85eac9d55a86d74d2e9d 100644
--- a/tools/telemetry/telemetry/core/browser.py
+++ b/tools/telemetry/telemetry/core/browser.py
@@ -203,6 +203,10 @@ class Browser(object):
         'CpuProcessTime': S,
         'TotalTime': T
       }
+      'Global': {
+        'GlobalCpuFrequencyStats': {
+        },
+      }
     }
     Any of the above keys may be missing on a per-platform basis.
     """
@@ -216,6 +220,11 @@ class Browser(object):
       if not len(result[process_type]):
         continue
       result[process_type].update(cpu_timestamp)
+
+    # Fetch system-wide CPU stats as well.
+    global_cpu_stats = self._platform_backend.GetGlobalCpuStats()
+    if global_cpu_stats:
+      result['Global'] = global_cpu_stats
     return result
 
   @property