[chromium] There is no Color(float, float, float) constructor, fix an attempt to...

[chromium] There is no Color(float, float, float) constructor, fix an attempt to call it.
https://bugs.webkit.org/show_bug.cgi?id=83920

Reviewed by James Robinson.

Found by clang:
  third_party/WebKit/Source/WebKit/chromium/tests/LayerChromiumTest.cpp:508:89:error: implicit conversion turns literal floating-point number into integer: 'float' to 'int' [-Werror,-Wliteral-conversion]
  EXECUTE_AND_VERIFY_SET_NEEDS_COMMIT_BEHAVIOR(1, testLayer->setBackgroundColor(Color(0.4f, 0.4f, 0.4f)));
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~

* tests/LayerChromiumTest.cpp:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114201 268f45cc-cd09-0410-ab3c-d52691b4dbfc