DevTools: Automagically detect user compiled content shell in npm test

third_party/WebKit/Source/devtools/readme.md

Index: third_party/WebKit/Source/devtools/readme.md
diff --git a/third_party/WebKit/Source/devtools/readme.md b/third_party/WebKit/Source/devtools/readme.md
index 7f0f34d30f0a9acbe20084248eed1f8f2f255674..92b3855a72e49bab8f0cc978651ad981488310d7 100644
--- a/third_party/WebKit/Source/devtools/readme.md
+++ b/third_party/WebKit/Source/devtools/readme.md
@@ -37,6 +37,20 @@ The frontend is available through a git subtree mirror on [chromium.googlesource
 * [awesome-chrome-devtools](https://github.com/paulirish/awesome-chrome-devtools): recommended tools and resources
 * Contributing to DevTools: [bit.ly/devtools-contribution-guide](http://bit.ly/devtools-contribution-guide)
 
+### Testing
+
+Basic:
+* `npm test` - builds devtools and runs all inspector layout tests
+
+> Note: If you're using a full chromium checkout and compiled content shell in out/Release, then `npm test` uses that. Otherwise, with only a front-end checkout (i.e. cloning from GitHub), then `npm test` will fetch a previously compiled content shell from the cloud (and cache it for future test runs).
+
+Advanced:
+* `npm test -- --fetch-content-shell` - even if you're using a full chromium checkout and have a compiled content shell, this will fetch a pre-compiled content shell. This is useful if you haven't compiled your content shell recently.
+* `npm test -- -f --child-processes=16` - pass in additional flags to the test harness
+* `npm test -- inspector/sources inspector/console` - run specific tests
+* `npm test -- inspector/cookie-resource-match.html --debug-devtools` - debug a specific test (non-bundled & minified). You can use "-d" as a shorthand for "--debug-devtools".
+* `npm run test:build` - only builds devtools (in debug mode)
+* `npm run test:run` - only runs devtools tests
 
 #### Development
 * All devtools commits: [View the log], [RSS feed] or [@DevToolsCommits] on Twitter