Break rtp_rtcp_format out of rtp_rtcp, to resolve circular dependencies

webrtc/modules/rtp_rtcp/source/rtp_header_extension_map.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_header_extension_map.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_header_extension_map.cc b/webrtc/modules/rtp_rtcp/source/rtp_header_extension_map.cc
index d65b11d5cf22a4d310986a7fe95bf76b4ead7615..3d48ef08bac7410a24a06b685a16875ebb25a0a6 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_header_extension_map.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_header_extension_map.cc
@@ -11,7 +11,6 @@
 #include "webrtc/modules/rtp_rtcp/include/rtp_header_extension_map.h"
 
 #include "webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h"
-#include "webrtc/modules/rtp_rtcp/source/rtp_utility.h"
 #include "webrtc/rtc_base/arraysize.h"
 #include "webrtc/rtc_base/checks.h"
 #include "webrtc/rtc_base/logging.h"
@@ -19,8 +18,6 @@
 namespace webrtc {
 namespace {
 
-using RtpUtility::Word32Align;
-
 struct ExtensionInfo {
   RTPExtensionType type;
   const char* uri;
@@ -102,7 +99,10 @@ size_t RtpHeaderExtensionMap::GetTotalLengthInBytes(
   }
   if (values_size == 0)
     return 0;
-  return Word32Align(kRtpOneByteHeaderLength + values_size);
+  size_t size = kRtpOneByteHeaderLength + values_size;
+  // Round up to the nearest size that is a multiple of 4.
+  // Which is same as round down (size + 3).
+  return size + 3 - (size + 3) % 4;

[eladalon, 2017/09/12 15:25:24]

I still think this would be safer, clearer and more efficient:
  return size & (std::numeric_limits<size_t>::max() - 3);
1. If I am not mistaken, bitwise-and will always be more efficient than modulo.
2. The left side of the binary-and operator is compile-time, not runtime,
computable.

[danilchap, 2017/09/12 15:40:31]

For any reasonable use (there are up to 16 types of extension each of up to 16
bytes long, so size is always very small) I find both solutions equally safe.

personally I find rounding with reminder clearer than rounding with bitwise
operator (last one rely on knowledge how integers are layed out in memory, first
one rely on a bit of math)

bitwise is more efficient, but extra efficiency I fine negligible.

 }
 
 int32_t RtpHeaderExtensionMap::Deregister(RTPExtensionType type) {