Add Android-backend to the memory_inspector (prerequisites).

tools/memory_inspector/memory_inspector/core/backends.py

Index: tools/memory_inspector/memory_inspector/core/backends.py
diff --git a/tools/memory_inspector/memory_inspector/core/backends.py b/tools/memory_inspector/memory_inspector/core/backends.py
index c5679ee30c3be680973626fbb102db97f4a869a7..b230dcb37cc20f0d23018807b5d2f32cefea5230 100644
--- a/tools/memory_inspector/memory_inspector/core/backends.py
+++ b/tools/memory_inspector/memory_inspector/core/backends.py
@@ -37,7 +37,7 @@ def GetDevice(backend_name, device_id):
 class Backend(object):
   """Base class for backends.
 
-    This is the extension point for the OS-specific profiler implementations.
+  This is the extension point for the OS-specific profiler implementations.
   """
 
   def __init__(self, settings=None):
@@ -68,6 +68,10 @@ class Device(object):
     # Initialize with empty settings if not required by the overriding device.
     self.settings = settings or Settings()
 
+  def Initialize(self):
+    """Called before anything else, for initial provisioning."""
+    raise NotImplementedError()
+
   def IsNativeAllocTracingEnabled(self):
     """Check if the device is ready to capture native allocation traces."""
     raise NotImplementedError()
@@ -92,6 +96,10 @@ class Device(object):
     """Returns an instance of |Process| or None (if not found)."""
     raise NotImplementedError()
 
+  def GetStats(self):
+    """Returns an instance of |DeviceStats|."""
+    raise NotImplementedError()
+
   @property
   def name(self):
     """Friendly name of the target device (e.g., phone model)."""
@@ -121,16 +129,54 @@ class Process(object):
     """Returns an instance of |native_heap.NativeHeap|."""
     raise NotImplementedError()
 
+  def GetStats(self):
+    """Returns an instance of |ProcessStats|."""
+    raise NotImplementedError()
+
   def __str__(self):
     return '[%d] %s' % (self.pid, self.name)
 
 
+class DeviceStats(object):
+  """CPU/Memory stats for a |Device|."""
+
+  def __init__(self, uptime, cpu_times, memory_stats):
+    """Args:
+      uptime: uptime in seconds.
+      cpu_times: array (CPUs) of dicts (cpu times since last call).
+          e.g., [{'User': 10, 'System': 80, 'Idle': 10}, ... ]
+      memory_stats: Dictionary of memory stats. e.g., {'Free': 1, 'Cached': 10}
+    """
+    assert(isinstance(cpu_times, list) and isinstance(cpu_times[0], dict))
+    assert(isinstance(memory_stats, dict))
+    self.uptime = uptime
+    self.cpu_times = cpu_times
+    self.memory_stats = memory_stats
+
+
+class ProcessStats(object):
+  """CPU/Memory stats for a |Process|."""
+
+  def __init__(self, threads, run_time, cpu_usage, vm_rss, page_faults):
+    """Args:
+      threads: Number of threads.
+      run_time: Total process uptime in seconds.
+      cpu_usage: CPU usage [0-100] since the last GetStats call.
+      vm_rss_kb: Resident Memory Set in Kb.
+      page_faults: Number of VM page faults (hard + soft).
+    """
+    self.threads = threads
+    self.run_time = run_time
+    self.cpu_usage = cpu_usage
+    self.vm_rss = vm_rss
+    self.page_faults = page_faults
+
+
 class Settings(object):
   """Models user-definable settings for backends and devices."""
 
   def __init__(self, expected_keys=None):
-    """
-    Args:
+    """Args:
       expected_keys: A dict. (key-name -> description) of expected settings
     """
     self.expected_keys = expected_keys or {}