Move code search info to sub-page. Add additional code search options.

site/dev/tools/codesearch.md

+Code Search
+===========
+
+There are a number of ways to search the Skia codebase, each with advantages and
+disadvantages.
+
+[cs.skia.org](http://cs.skia.org) redirects to
+[Chromium code search](https://code.google.com/p/chromium/codesearch) restricted
+to the Skia portion of the Chromium tree. You can add a query after the slash;
+e.g. [cs.skia.org/foo](http://cs.skia.org/foo) will search for "foo" within the
+Skia tree. Chromium code search provides cross-references, but not
+history/blame.
+
+For Googlers, there is also the option of
+[the skia depot](https://cs.corp.google.com/#skia/) in internal Code Search. In
+addition to the main [skia](https://cs.corp.google.com/#skia/skia/) repo,
+internal Code Search indexes the
+[buildbot](https://cs.corp.google.com/#skia/buildbot/),
+[common](https://cs.corp.google.com/#skia/common/), and
+[skia_internal](https://cs.corp.google.com/#skia/skia_internal/) repos. However,
+cross-references, history/blame, and code analysis are not available.
+
+The Github mirrors of the [skia](https://github.com/google/skia) and
+[skia-buildbot](https://github.com/google/skia-buildbot) repos are useful for
+investigating history and blame, or for exploring release branches or other
+branches. However, the search functionality is fairly limited, cross-references
+are not available, and in history the original committer's username is replaced
+with that person's Github username.
+
+You can also navigate through the
+[Skia repos on googlesource.com](https://skia.googlesource.com/). All commits
+appear here first.
+
+  Code search option  |Search |XRef |History |Repos                         |Branches |Freshness
+  --------------------|-------|-----|--------|------------------------------|---------|----------------------
+  [cs.skia.org][1]    |regexp | yes |no      |skia                          |master   |last DEPS roll + hours
+  [Internal][2]       |regexp | no  |no      |skia buildbot common internal |master   |hours
+  [Github][3]         |basic  | no  |yes     |skia buildbot                 |all      |hour
+  [googlesource][4]   |none   | no  |yes     |all                           |all      |N/A
+
+[1]: http://cs.skia.org/               "Chromium code search"
+[2]: https://cs.corp.google.com/#skia/ "Internal Code Search"
+[3]: https://github.com/google/skia    "Github mirror of skia"
+[4]: https://skia.googlesource.com/    "Master Skia repos on googlesource.com"