Fix CQ keyword and add more detail

site/dev/contrib/cqkeywords.md

 Commit Queue Keywords
 =====================
 
 COMMIT
 ------
 
 If you are working on experimental code and do not want to risk accidentally
 submitting the change via the CQ, then you can mark it with "COMMIT=false".
 The CQ will immediately abandon the change if it contains this option.
 To do a dry run through the CQ please use Rietveld's [dry run](https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/G5-X0_tfmok) feature.
 
     COMMIT=false
 
 The CQ will run through its list of verifiers (reviewer check, trybots, tree check, 
 presubmit check), and will close the issue instead of committing it.
 
-    NO_DEPENDENCY_CHECK=true
+    NO_DEPENDENCY_CHECKS=true
 
-The CQ rejects patchsets with open dependencies. You can skip this check with this keyword.
+The CQ rejects patchsets with open dependencies. An open dependency exists when a CL
+depends on another CL that is not yet closed. You can skip this check with this keyword.
 
     CQ_INCLUDE_TRYBOTS
 
 Allows you to add arbitrary trybots to the CQ's list of default trybots. 
 The CQ will block till these tryjobs pass just like the default list of tryjobs.
 
 This is the format of the values of this keyword:
 
     CQ_INCLUDE_TRYBOTS=master1:bot1,bot2;master2:bot3,bot4
 
@@ skipping 72 matching lines @@
 The CQ will then not run any try jobs for your change and will commit the CL as soon as the tree is open, assuming the presubmit check passes.
 
 NO_MERGE_BUILDS
 ---------------
 
 This keyword prevents the Skia build masters from building this commit with others. Use it when your
 commit may have effects that you don't want mis-attributed to other commits. Just include the keyword
 somewhere in the commit message:
 
     NO_MERGE_BUILDS