Replace av_malloc with AlignedAlloc for memory allocation in DecoderBuffer.

media/base/decoder_buffer.h

Index: media/base/decoder_buffer.h
diff --git a/media/base/decoder_buffer.h b/media/base/decoder_buffer.h
index e822de555c623227da160885a94d531bdb561428..165f473d6513494280c45ebaf7453f81b37327c8 100644
--- a/media/base/decoder_buffer.h
+++ b/media/base/decoder_buffer.h
@@ -21,6 +21,15 @@ namespace media {
 
 class MEDIA_EXPORT DecoderBuffer : public Buffer {
  public:
+  enum {
+    kPaddingSize = 16,
+#if defined(ARCH_CPU_ARM_FAMILY)
+    kAlignmentSize = 16
+#else
+    kAlignmentSize = 32
+#endif
+  };
+
   // Allocates buffer of size |buffer_size| >= 0.  Buffer will be padded and
   // aligned as necessary.
   explicit DecoderBuffer(int buffer_size);