Tool added to extract network traffic annotations.

tools/clang/traffic_annotation_extractor/README.txt

Index: tools/clang/traffic_annotation_extractor/README.txt
diff --git a/tools/clang/traffic_annotation_extractor/README.txt b/tools/clang/traffic_annotation_extractor/README.txt
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index 0000000000000000000000000000000000000000..1cc1e7e5ebe7024537118aa3816e9d42ecf07bf0
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+++ b/tools/clang/traffic_annotation_extractor/README.txt
@@ -0,0 +1,17 @@
+This is a clang tool to extract network traffic annotations. The tool is run by
+tools/traffic_annotation/traffic_annotaion_auditor. Refer to it for help on how
+to use.
+
+Build on Linux, run:
+tools/clang/scripts/update.py --bootstrap --force-local-build
+  --without-android --tools blink_gc_plugin plugins
+  rewrite_to_chrome_style traffic_annotation_extractor
+
+Build on Window:
+1. Either open a "VS2015 x64 Native Tools Command Prompt", or open a normal
+   command prompt and run "depot_tools\win_toolchain\vs_fies\

[Peter Kasting, 2016/11/23 17:01:52]

Typo (fies).  But assume people are using a command prompt that has the MSVC
tools set up in the environment, as that's what our setup steps will produce,
and not doing this makes all kinds of stuff break; so just omit this step. 
Given that the second step is just the same as the Linux instructions with the
addition of "python" in front, I'd omit that too (we assume in various places
Windows developers have either set up their environment to be able to launch
python scripts directly, or know to prepend "python" when doing so).

+   $long_autocompleted_hash\win_sdk\bin\setenv.cmd /x64"
+2. Run python tools/clang/scripts/update.py --bootstrap --force-local-build
+   --without-android --tools blink_gc_plugin plugins rewrite_to_chrome_style
+   traffic_annotation_extractor
+