The code is written as if the compositor thread could also call callOnCompositingRunLoop() which makes the code confusing.
Created attachment 280912 [details]
Attachment 280912 [details] did not pass style-queue:
ERROR: Source/WebKit2/Shared/CoordinatedGraphics/threadedcompositor/CompositingRunLoop.h:49: Extra space before ( in function call [whitespace/parens] 
ERROR: Source/WebKit2/Shared/CoordinatedGraphics/threadedcompositor/CompositingRunLoop.cpp:44: Extra space before ( in function call [whitespace/parens] 
Total errors found: 2 in 4 files
If any of these errors are false positives, please file a bug against check-webkit-style.
Committed r201922: <http://trac.webkit.org/changeset/201922>