Bug 1074738 - GetCurrentDoc fixes in content/base, r=wchen

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extra : rebase_source : 5bd87b39f04e5cef229e8e15bc2bf56aef9c5995
Bug 1075279 - GetCurrentDoc fixes in content/html, r=wchen

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extra : rebase_source : ad4f485b2346d629b84e6c1558c24615fdf8d29b
Bug 1075050 - GetCurrentDoc fixes in content/xul, r=wchen

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extra : rebase_source : a1c88534d0beebd1618e0b15249c778470d65c82
Bug 1075125 - GetCurrentDoc fixes in content/svg, r=wchen

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extra : rebase_source : 72ca9c3f48b54ca7eaf4eefd061b06fad0f37385