Add coverage

tools/telemetry/third_party/coverage/coverage/monkey.py

Index: tools/telemetry/third_party/coverage/coverage/monkey.py
diff --git a/tools/telemetry/third_party/coverage/coverage/monkey.py b/tools/telemetry/third_party/coverage/coverage/monkey.py
new file mode 100644
index 0000000000000000000000000000000000000000..c4ec68c66807a147ec095b36f21f681ac584a30e
--- /dev/null
+++ b/tools/telemetry/third_party/coverage/coverage/monkey.py
@@ -0,0 +1,50 @@
+# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
+# For details: https://bitbucket.org/ned/coveragepy/src/default/NOTICE.txt
+
+"""Monkey-patching to make coverage.py work right in some cases."""
+
+import multiprocessing
+import multiprocessing.process
+import sys
+
+# An attribute that will be set on modules to indicate that they have been
+# monkey-patched.
+PATCHED_MARKER = "_coverage$patched"
+
+
+def patch_multiprocessing():
+    """Monkey-patch the multiprocessing module.
+
+    This enables coverage measurement of processes started by multiprocessing.
+    This is wildly experimental!
+
+    """
+    if hasattr(multiprocessing, PATCHED_MARKER):
+        return
+
+    if sys.version_info >= (3, 4):
+        klass = multiprocessing.process.BaseProcess
+    else:
+        klass = multiprocessing.Process
+
+    original_bootstrap = klass._bootstrap
+
+    class ProcessWithCoverage(klass):
+        """A replacement for multiprocess.Process that starts coverage."""
+        def _bootstrap(self):
+            """Wrapper around _bootstrap to start coverage."""
+            from coverage import Coverage
+            cov = Coverage(data_suffix=True)
+            cov.start()
+            try:
+                return original_bootstrap(self)
+            finally:
+                cov.stop()
+                cov.save()
+
+    if sys.version_info >= (3, 4):
+        klass._bootstrap = ProcessWithCoverage._bootstrap
+    else:
+        multiprocessing.Process = ProcessWithCoverage
+
+    setattr(multiprocessing, PATCHED_MARKER, True)