Create DevToolsHttp and basic DevToolsClientBackend.

tools/telemetry/telemetry/core/backends/chrome_inspector/devtools_client_backend.py

Index: tools/telemetry/telemetry/core/backends/chrome_inspector/devtools_client_backend.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome_inspector/devtools_client_backend.py b/tools/telemetry/telemetry/core/backends/chrome_inspector/devtools_client_backend.py
new file mode 100644
index 0000000000000000000000000000000000000000..0489927e5d141a0d3a50b45642c2c9b6f9872ff2
--- /dev/null
+++ b/tools/telemetry/telemetry/core/backends/chrome_inspector/devtools_client_backend.py
@@ -0,0 +1,57 @@
+# 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 re
+
+from telemetry import decorators
+from telemetry.core.backends.chrome_inspector import devtools_http
+
+
+class DevToolsClientBackend(object):
+  def __init__(self, devtools_port):
+    self._devtools_port = devtools_port
+    self._devtools_http = devtools_http.DevToolsHttp(devtools_port)
+    self._tracing_backend = None
+
+  # TODO(chrishenry): This is temporarily exposed during DevTools code
+  # refactoring. Please do not introduce new usage! crbug.com/423954
+  @property
+  def devtools_http(self):
+    return self._devtools_http
+
+  def IsAlive(self):
+    """Whether the DevTools server is available and connectable."""
+    try:
+      self._devtools_http.Request('', timeout=.1)
+    except devtools_http.DevToolsClientConnectionError:
+      return False
+    else:
+      return True
+
+  @decorators.Cache
+  def GetChromeBranchNumber(self):
+    # Detect version information.
+    resp = self._devtools_http.RequestJson('version')
+    if 'Protocol-Version' in resp:
+      if 'Browser' in resp:
+        branch_number_match = re.search(r'Chrome/\d+\.\d+\.(\d+)\.\d+',
+                                        resp['Browser'])
+      else:
+        branch_number_match = re.search(
+            r'Chrome/\d+\.\d+\.(\d+)\.\d+ (Mobile )?Safari',
+            resp['User-Agent'])
+
+      if branch_number_match:
+        branch_number = int(branch_number_match.group(1))
+        if branch_number:
+          return branch_number
+
+    # Branch number can't be determined, so fail any branch number checks.
+    return 0
+
+  # TODO(chrishenry): This is exposed tempoarily during DevTools code
+  # refactoring. Instead, we should expose InspectorBackendList or
+  # equivalent. crbug.com/423954.
+  def ListInspectableContexts(self):
+    return self._devtools_http.RequestJson('')