Bug 1023677 - Mark BasicCompositor as not supporting component alpha layers. r=roc
Bug 1023677 - Don't repeat layer building if there was only a single layer. r=roc
Bug 1023677 - Don't set mSupportComponentAlphaChildren unless we actually have them. r=roc
Bug 1023677 - Don't flatten active transform layers. r=roc
Bug 1039145 - Part 1: Clean up AreComponentAlphaLayersEnabled. r=roc
Bug 1039145 - Part 2: Fully remove component alpha/background copying support from BasicCompositor. r=roc