Use size_t more consistently for packet/payload lengths.

See design doc at https://docs.google.com/a/chromium.org/document/d/1I6nmE9D_BmCY-IoV6MDPY2V6WYpEI-dg2apWXTfZyUI/edit?usp=sharing for more information.

This CL was reviewed and approved in pieces in the following CLs:
https://webrtc-codereview.appspot.com/24209004/
https://webrtc-codereview.appspot.com/24229004/
https://webrtc-codereview.appspot.com/24259004/
https://webrtc-codereview.appspot.com/25109004/
https://webrtc-codereview.appspot.com/26099004/
https://webrtc-codereview.appspot.com/27069004/
https://webrtc-codereview.appspot.com/27969004/
https://webrtc-codereview.appspot.com/27989004/
https://webrtc-codereview.appspot.com/29009004/
https://webrtc-codereview.appspot.com/30929004/
https://webrtc-codereview.appspot.com/30939004/
https://webrtc-codereview.appspot.com/31999004/
Committing as TBR to the original reviewers.

BUG=chromium:81439
TEST=none
TBR=pthatcher,henrik.lundin,tina.legrand,stefan,tkchin,glaznev,kjellander,perkj,mflodman,henrika,asapersson,niklas.enbom

Review URL: https://webrtc-codereview.appspot.com/23129004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7726 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/system_wrappers/source/file_impl.cc b/webrtc/system_wrappers/source/file_impl.cc
index 8b21b96..eb199a8 100644
--- a/webrtc/system_wrappers/source/file_impl.cc
+++ b/webrtc/system_wrappers/source/file_impl.cc
@@ -187,19 +187,16 @@
   return 0;
 }
 
-int FileWrapperImpl::Read(void* buf, int length) {
+int FileWrapperImpl::Read(void* buf, size_t length) {
   WriteLockScoped write(*rw_lock_);
-  if (length < 0)
-    return -1;
-
   if (id_ == NULL)
     return -1;
 
-  int bytes_read = static_cast<int>(fread(buf, 1, length, id_));
+  size_t bytes_read = fread(buf, 1, length, id_);
   if (bytes_read != length && !looping_) {
     CloseFileImpl();
   }
-  return bytes_read;
+  return static_cast<int>(bytes_read);
 }
 
 int FileWrapperImpl::WriteText(const char* format, ...) {
@@ -226,14 +223,11 @@
   }
 }
 
-bool FileWrapperImpl::Write(const void* buf, int length) {
+bool FileWrapperImpl::Write(const void* buf, size_t length) {
   WriteLockScoped write(*rw_lock_);
   if (buf == NULL)
     return false;
 
-  if (length < 0)
-    return false;
-
   if (read_only_)
     return false;
 
diff --git a/webrtc/system_wrappers/source/file_impl.h b/webrtc/system_wrappers/source/file_impl.h
index 1abf010..bed692b 100644
--- a/webrtc/system_wrappers/source/file_impl.h
+++ b/webrtc/system_wrappers/source/file_impl.h
@@ -44,8 +44,8 @@
   virtual int SetMaxFileSize(size_t bytes) OVERRIDE;
   virtual int Flush() OVERRIDE;
 
-  virtual int Read(void* buf, int length) OVERRIDE;
-  virtual bool Write(const void* buf, int length) OVERRIDE;
+  virtual int Read(void* buf, size_t length) OVERRIDE;
+  virtual bool Write(const void* buf, size_t length) OVERRIDE;
   virtual int WriteText(const char* format, ...) OVERRIDE;
   virtual int Rewind() OVERRIDE;