clovis: Identify prefetchable resources from dependencies and tracing.

tools/android/loading/request_dependencies_lens.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Gathers and infers dependencies between requests.
 
 When executed as a script, loads a trace and outputs the dependencies.
 """
 
 import collections
@@ skipping 12 matching lines @@
   def __init__(self, trace):
     """Initializes an instance of RequestDependencyLens.
 
     Args:
       trace: (LoadingTrace) Loading trace.
     """
     self.loading_trace = trace
     self._requests = self.loading_trace.request_track.GetEvents()
     self._requests_by_id = {r.request_id: r for r in self._requests}
     self._requests_by_url = collections.defaultdict(list)
+    self._deps = None
     for request in self._requests:
       self._requests_by_url[request.url].append(request)
     self._frame_to_parent = {}
     for event in self.loading_trace.page_track.GetEvents():
       if event['method'] == 'Page.frameAttached':
         self._frame_to_parent[event['frame_id']] = event['parent_frame_id']
 
   def GetRequestDependencies(self):
     """Returns a list of request dependencies.
 
     Returns:
       [(first, second, reason), ...] where first and second are instances of
       request_track.Request, and reason is in DEPENDENCIES. The second request
       depends on the first one, with the listed reason.
     """
-    deps = []
+    self._ComputeRequestDependencies()
+    return copy.copy(self._deps)
+
+  def GetRedirectChain(self, request):
+    """Returns the whole redirect chain for a given request.
+
+    Note that this misses some JS-based redirects.
+
+    Returns:
+      A list of request, containing the request passed as a parameter.
+    """
+    self._ComputeRequestDependencies()
+    chain = [request]
+    while True:
+      for (first_request, second_request, why) in self._deps:
+        if first_request == request and why == 'redirect':
+          chain.append(second_request)
+          request = second_request
+          break
+      else:
+        return chain
+
+  def _ComputeRequestDependencies(self):
+    if self._deps is not None:
+      return
+    self._deps = []
     for request in self._requests:
       dependency = self._GetDependency(request)
       if dependency:
-        deps.append(dependency)
-    return deps
+        self._deps.append(dependency)
 
   def _GetDependency(self, request):
     """Returns (first, second, reason), or None.
 
     |second| depends on |first|.
 
     Args:
       request: (Request) the request we wish to get the initiator of.
 
     Returns:
@@ skipping 151 matching lines @@
 if __name__ == '__main__':
   import json
   import sys
   trace_filename = sys.argv[1]
   json_dict = json.load(open(trace_filename, 'r'))
   lens = RequestDependencyLens(
       loading_trace.LoadingTrace.FromJsonDict(json_dict))
   depedencies = lens.GetRequestDependencies()
   for (first, second, dep_reason) in depedencies:
     print '%s -> %s\t(%s)' % (first.request_id, second.request_id, dep_reason)