Bug 614732 part 2 - Doc changes (clarify why nsDisplayTransform requires a bounds rect, and correctly associate nsStyleTransformMatrix's doxygen comment with it). r=roc.

layout/base/nsDisplayList.h

@@ -2046,9 +2046,15 @@ private:
 };
 #endif
 
-/* A display item that applies a transformation to all of its descendent
+/* A display item that applies a transformation to all of its descendant
  * elements.  This wrapper should only be used if there is a transform applied
  * to the root element.
+ *
+ * The reason that a "bounds" rect is involved in transform calculations is
+ * because CSS-transforms allow percentage values for the x and y components
+ * of <translation-value>s, where percentages are percentages of the element's
+ * content box.
+ *
  * INVARIANT: The wrapped frame is transformed.
  * INVARIANT: The wrapped frame is non-null.
  */ 

layout/style/nsStyleTransformMatrix.h

@@ -46,6 +46,8 @@
 #include "nsRect.h"
 
 struct nsCSSValueList;
+class nsStyleContext;
+class nsPresContext;
 
 /**
  * A class representing a style transformation matrix.  The class actually
@@ -62,8 +64,6 @@ struct nsCSSValueList;
  * Note that unlike the Thebes gfxMatrix, vectors are column vectors and
  * consequently the multiplication of a matrix A and a vector x is Ax, not xA.
  */
-class nsStyleContext;
-class nsPresContext;
 class nsStyleTransformMatrix
 {
  public: