YUV software decode path stride fixes.

base/bits.h

Index: base/bits.h
diff --git a/base/bits.h b/base/bits.h
index b2209e8ed7934a6dfc918c3d7d12b9c455f594e1..9383f8832408c7da40fa47ec49a4325c778f89ac 100644
--- a/base/bits.h
+++ b/base/bits.h
@@ -41,6 +41,16 @@ inline int Log2Ceiling(uint32 n) {
   }
 }
 
+// Returns the largest i such as i <= n and i == k * mul for some integer k
+inline uint32 RoundDown(uint32 n, uint32 mul) {
+  return (n / mul) * mul;
+}
+
+// Returns the smallest i such as i >= n and i == k * mul for some integer k
+inline uint32 RoundUp(uint32 n, uint32 mul) {
+  return (n + (mul - 1)) / mul * mul;

[jar (doing other things), 2012/11/20 22:54:35]

Does this do what you want when:
n + mul - 1 > UINT_MAX?

[sheu, 2012/11/20 23:13:50]

It doesn't but I don't really have other suggestions for this, besides
increasing the width of the intermediate.  O don't believe we'll be rounding to
anything excessive -- maybe DCHECK this?

+}
+
 }  // namespace bits
 }  // namespace base