Replace 'test_shell' with 'DumpRenderTree' in docs README

chrome/common/extensions/docs/README.txt

Index: chrome/common/extensions/docs/README.txt
diff --git a/chrome/common/extensions/docs/README.txt b/chrome/common/extensions/docs/README.txt
index b05621026dd0ddba5d470570adff12607afb706e..ea0c0fa21a5de6533a0d77770131f64e6c123c30 100644
--- a/chrome/common/extensions/docs/README.txt
+++ b/chrome/common/extensions/docs/README.txt
@@ -35,10 +35,10 @@ To build the extension docs, run the build.py script in the ./build directory.
 This will regenerate the docs and report which, if any, files have changed
 and need to be included in the changelist that changed the dependent files.
 
-Note that the build.py script depends on test_shell to run, so you must be
-able to build test_shell to build extension_docs. The build.py script will
-look in typical locations for the test_shell executable, but you may set
-the path to test_shell explicitly with --test-shell-path.
+Note that the build.py script depends on DumpRenderTree to run, so you must be
+able to build DumpRenderTree to build extension_docs. The build.py script will
+look in typical locations for the DumpRenderTree executable, but you may set
+the path to DumpRenderTree explicitly with --dump-render-tree-path.
 
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 Design