Bug 921174 part 1: Rename reflow state variables in nsHTMLButtonFrame, for clarity. r=bz
Bug 921174 part 2: Use a separate nsReflowStatus for button frame's reflow vs. button contents frame's reflow. r=bz
Bug 921174 part 3: Make ReflowButtonContents() use a dedicated nsHTMLReflowMetrics instance, and give it full responsibility for populating parent's metrics. r=bz
Bug 921174 part 4: Move focusPadding into ReflowButtonContents, the only place it's used now. r=bz
Bug 921174 part 5: Assert that nsHTMLButtonControlFrame has exactly one child, and it's the button-content frame. r=bz
(no bug) Remove useless "color" declaration (overridden by another "color" declaration several lines below it) from vertical-centering button reftest.