Make telemetry platform a singleton

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 c317e6a248068e21278e08fa0d926c4ae8925050..19ca2d3ab7b1c7e7e661a22cb772cacf2f20e983 100644
--- a/tools/telemetry/telemetry/core/browser.py
+++ b/tools/telemetry/telemetry/core/browser.py
@@ -10,7 +10,7 @@ from telemetry.core import exceptions
 from telemetry.core import extension_dict
 from telemetry.core import local_server
 from telemetry.core import memory_cache_http_server
-from telemetry.core import platform
+from telemetry.core import platform as platform_module
 from telemetry.core import tab_list
 from telemetry.core import wpr_modes
 from telemetry.core import wpr_server
@@ -29,12 +29,12 @@ class Browser(object):
     with browser_to_create.Create() as browser:
       ... do all your operations on browser here
   """
-  def __init__(self, backend, platform_backend):
+  def __init__(self, backend, platform):
+    assert isinstance(platform, platform_module.Platform)
     self._browser_backend = backend
     self._http_server = None
     self._wpr_server = None
-    self._platform_backend = platform_backend
-    self._platform = platform.Platform(platform_backend)
+    self._platform = platform
     self._active_profilers = []
     self._profilers_states = {}
     self._local_server_controller = local_server.LocalServerController(backend)
@@ -101,6 +101,7 @@ class Browser(object):
     return profiler_name in [profiler.name() for
                              profiler in self._active_profilers]
 
+
   def _GetStatsCommon(self, pid_stats_function):
     browser_pid = self._browser_backend.pid
     result = {
@@ -110,9 +111,9 @@ class Browser(object):
         'Other': {'ProcessCount': 0}
     }
     process_count = 1
-    for child_pid in self._platform_backend.GetChildPids(browser_pid):
+    for child_pid in self._platform.GetChildPids(browser_pid):
       try:
-        child_cmd_line = self._platform_backend.GetCommandLine(child_pid)
+        child_cmd_line = self._platform.GetCommandLine(child_pid)
         child_stats = pid_stats_function(child_pid)
       except exceptions.ProcessGoneException:
         # It is perfectly fine for a process to have gone away between calling
@@ -175,14 +176,15 @@ class Browser(object):
     }
     Any of the above keys may be missing on a per-platform basis.
     """
-    self._platform_backend.PurgeUnpinnedMemory()
-    result = self._GetStatsCommon(self._platform_backend.GetMemoryStats)
+    self._platform.WillGetMemoryStats()
+    result = self._GetStatsCommon(self._platform.GetMemoryStats)
     result['SystemCommitCharge'] = \
-        self._platform_backend.GetSystemCommitCharge()
+        self._platform.GetSystemCommitCharge()
     result['SystemTotalPhysicalMemory'] = \
-        self._platform_backend.GetSystemTotalPhysicalMemory()
+        self._platform.GetSystemTotalPhysicalMemory()
     return result
 
+
   @property
   def cpu_stats(self):

[tonyg, 2014/08/02 15:58:18]

I think the root of the problem here is that these *_stats methods don't belong
on Browser. Instead, they should be available via Timeline.

The unfortunate thing about this patch's attempt to make these first class
citizens in Platform is that it means opening up all these things in the
Platform API more widely. WDYT?

     """Returns a dict of cpu statistics for the system.
@@ -201,11 +203,11 @@ class Browser(object):
     }
     Any of the above keys may be missing on a per-platform basis.
     """
-    result = self._GetStatsCommon(self._platform_backend.GetCpuStats)
+    result = self._GetStatsCommon(self._platform.GetCpuStats)
     del result['ProcessCount']
 
     # We want a single time value, not the sum for all processes.
-    cpu_timestamp = self._platform_backend.GetCpuTimestamp()
+    cpu_timestamp = self._platform.GetCpuTimestamp()
     for process_type in result:
       # Skip any process_types that are empty
       if not len(result[process_type]):
@@ -236,7 +238,7 @@ class Browser(object):
       }
     }
     """
-    result = self._GetStatsCommon(self._platform_backend.GetIOStats)
+    result = self._GetStatsCommon(self._platform.GetIOStats)
     del result['ProcessCount']
     return result
 
@@ -254,9 +256,12 @@ class Browser(object):
     if not profiler_class in self._profilers_states:
       self._profilers_states[profiler_class] = {}
 
-    self._active_profilers.append(
-        profiler_class(self._browser_backend, self._platform_backend,
-            base_output_file, self._profilers_states[profiler_class]))
+    profiler = self.platform.InstantiateProfiler(
+        profiler_class,
+        self._browser_backend,
+        base_output_file,
+        self._profilers_states[profiler_class])
+    self._active_profilers.append(profiler)
 
   def StopProfiling(self):
     """Stops all active profilers and saves their results.
@@ -298,9 +303,9 @@ class Browser(object):
 
   def Close(self):
     """Closes this browser."""
-    for profiler_class in self._profilers_states:
-      profiler_class.WillCloseBrowser(self._browser_backend,
-                                      self._platform_backend)
+    profiler_classes = list(self._profilers_states.keys())
+    self._platform.WillCloseBrowser(self._browser_backend,
+                                    profiler_classes)
 
     self.platform.SetFullPerformanceModeEnabled(False)