[Telemetry] Add capability for values to reference external files.

tools/telemetry/telemetry/value/trace.py

Index: tools/telemetry/telemetry/value/trace.py
diff --git a/tools/telemetry/telemetry/value/trace.py b/tools/telemetry/telemetry/value/trace.py
new file mode 100644
index 0000000000000000000000000000000000000000..118098b838c0ae7793caf21c3bfc9a84819db891
--- /dev/null
+++ b/tools/telemetry/telemetry/value/trace.py
@@ -0,0 +1,82 @@
+# Copyright 2014 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.
+
+import os
+import tempfile
+
+from telemetry import value as value_module
+from telemetry.util import file_handle
+import telemetry.web_components # pylint: disable=W0611
+from trace_viewer.build import trace2html
+
+class TraceValue(value_module.Value):
+  def __init__(self, page, name, timeline_data, important=False,
+               description=None):
+    """A value that contains a TimelineData object and knows how to output it.
+
+    Adding TraceValues and outputting as JSON will produce a directory full of
+    HTML files called trace_files. Outputting as chart JSON will also produce
+    an index, files.html, linking to each of these files.
+    """
+    super(TraceValue, self).__init__(page, name, 'trace', important,
+                                     description)
+
+    tf = tempfile.NamedTemporaryFile()
+    timeline_data.Serialize(tf)
+    tf.flush()
+    os.fsync(tf)
+
+    tf2 = tempfile.NamedTemporaryFile()
+    trace2html.WriteHTMLForTracesToFile([tf.name], tf2)
+    tf2.flush()
+    os.fsync(tf2)
+
+    tf.close()
+
+    self._file_handle = file_handle.FromTempFile(tf2)
+
+  def GetAssociatedFileHandle(self):
+    return self._file_handle
+
+  def __repr__(self):
+    if self.page:
+      page_name = self.page.url
+    else:
+      page_name = None
+    return 'TraceValue(%s, %s)' % (page_name, self.name)
+
+  def GetBuildbotDataType(self, output_context):
+    return None
+
+  def GetBuildbotValue(self):
+    return None
+
+  def GetRepresentativeNumber(self):
+    return None
+
+  def GetRepresentativeString(self):
+    return None
+
+  @staticmethod
+  def GetJSONTypeName():
+    return 'trace'
+
+  @classmethod
+  def MergeLikeValuesFromSamePage(cls, values):
+    # TODO(eakuefner): Implement a MultiTraceValue: a Polymer-based,
+    # componentized, MultiTraceViwer-backed representation of more than one
+    # trace.
+    assert len(values) > 0
+    return values[0]
+
+  @classmethod
+  def MergeLikeValuesFromDifferentPages(cls, values,
+                                        group_by_name_suffix=False):
+    return None
+
+  def AsDict(self):
+    d = super(TraceValue, self).AsDict()
+    d['file_id'] = self._file_handle.id
+
+    return d