Bug 1014280 - Add a background color attribute to scrollable ContainerLayers. r=tn,BenWa

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extra : source : dff750e410e5f4e1ed019527ea17f37e53dd8fe6
Bug 1014280 - Fill blank areas created by overscroll transform with background color. r=mattwoodrow,BenWa,nical

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extra : source : 4323c71f0e921b50a1774e46ec700b354b479c7a