Replace av_malloc with AlignedAlloc for memory allocation in DecoderBuffer.

media/ffmpeg/ffmpeg_common.cc

Index: media/ffmpeg/ffmpeg_common.cc
diff --git a/media/ffmpeg/ffmpeg_common.cc b/media/ffmpeg/ffmpeg_common.cc
index b6690cb5f74d103e11e9c86f9eae50327ea1f2aa..00d91f552bb7fd62689ce61ec91a048697130821 100644
--- a/media/ffmpeg/ffmpeg_common.cc
+++ b/media/ffmpeg/ffmpeg_common.cc
@@ -4,11 +4,32 @@
 
 #include "media/ffmpeg/ffmpeg_common.h"
 
+#include "base/basictypes.h"
 #include "base/logging.h"
+#include "media/base/decoder_buffer.h"
 #include "media/base/video_util.h"
 
 namespace media {
 
+// Why FF_INPUT_BUFFER_PADDING_SIZE? FFmpeg assumes all input buffers are
+// padded. Check here to ensure FFmpeg only receives data padded to its
+// specifications.
+COMPILE_ASSERT(DecoderBuffer::kPaddingSize >= FF_INPUT_BUFFER_PADDING_SIZE,
+               decoder_buffer_padding_size_does_not_fit_ffmpeg_requirement);
+
+// Alignment requirement by FFmpeg for input buffers. This need to be updated
+// to match FFmpeg when it changes.
+#if defined(ARCH_CPU_ARM_FAMILY)
+static const int kFFmpegInputBufferAlignmentSize = 16;
+#else
+static const int kFFmpegInputBufferAlignmentSize = 32;
+#endif
+// Check here to ensure FFmpeg only receives data aligned to its specifications.
+COMPILE_ASSERT(
+    DecoderBuffer::kAlignmentSize >= kFFmpegInputBufferAlignmentSize &&
+    DecoderBuffer::kAlignmentSize % kFFmpegInputBufferAlignmentSize == 0,
+    decoder_buffer_alignment_size_does_not_fit_ffmpeg_requirement);
+
 static const AVRational kMicrosBase = { 1, base::Time::kMicrosecondsPerSecond };
 
 base::TimeDelta ConvertFromTimeBase(const AVRational& time_base,