Fix for mozilla target.

Make it a 'component' target. Otherwise, things can get really bad:

They led to ComplexTextInputPanel being defined in several components in
a components build:

objc[67340]: Class ComplexTextInputPanel is implemented in both
/Users/thakis/src/chrome/src/out/Release/./libcontent.dylib and
/Users/thakis/src/chrome/src/out/Release/libchrome_main_dll.dylib. One
of the
two will be used. Which one is undefined.

BUG=299841
R=thakis@chromium.org,mark@chromium.org

Review URL: https://codereview.chromium.org/121483002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242697 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242697