Replace NULL with nullptr in all C++ files.

webrtc/base/diskcache.cc

Index: webrtc/base/diskcache.cc
diff --git a/webrtc/base/diskcache.cc b/webrtc/base/diskcache.cc
index 2747018d17473547d2c3bab52884c336b865f999..a80aa457cd85491a95c09b70eebb1a12f3709ed6 100644
--- a/webrtc/base/diskcache.cc
+++ b/webrtc/base/diskcache.cc
@@ -111,7 +111,7 @@ bool DiskCache::LockResource(const std::string& id) {
 StreamInterface* DiskCache::WriteResource(const std::string& id, size_t index) {
   Entry* entry = GetOrCreateEntry(id, false);
   if (LS_LOCKED != entry->lock_state)
-    return NULL;
+    return nullptr;
 
   size_t previous_size = 0;
   std::string filename(IdToFilename(id, index));
@@ -122,9 +122,9 @@ StreamInterface* DiskCache::WriteResource(const std::string& id, size_t index) {
   }
 
   std::unique_ptr<FileStream> file(new FileStream);
-  if (!file->Open(filename, "wb", NULL)) {
+  if (!file->Open(filename, "wb", nullptr)) {
     LOG_F(LS_ERROR) << "Couldn't create cache file";
-    return NULL;
+    return nullptr;
   }
 
   entry->streams = std::max(entry->streams, index + 1);
@@ -155,13 +155,13 @@ StreamInterface* DiskCache::ReadResource(const std::string& id,
                                          size_t index) const {
   const Entry* entry = GetEntry(id);
   if (LS_UNLOCKED != entry->lock_state)
-    return NULL;
+    return nullptr;
   if (index >= entry->streams)
-    return NULL;
+    return nullptr;
 
   std::unique_ptr<FileStream> file(new FileStream);
-  if (!file->Open(IdToFilename(id, index), "rb", NULL))
-    return NULL;
+  if (!file->Open(IdToFilename(id, index), "rb", nullptr))
+    return nullptr;
 
   entry->accessors += 1;
   total_accessors_ += 1;
@@ -170,12 +170,12 @@ StreamInterface* DiskCache::ReadResource(const std::string& id,
 
 bool DiskCache::HasResource(const std::string& id) const {
   const Entry* entry = GetEntry(id);
-  return (NULL != entry) && (entry->streams > 0);
+  return (nullptr != entry) && (entry->streams > 0);
 }
 
 bool DiskCache::HasResourceStream(const std::string& id, size_t index) const {
   const Entry* entry = GetEntry(id);
-  if ((NULL == entry) || (index >= entry->streams))
+  if ((nullptr == entry) || (index >= entry->streams))
     return false;
 
   std::string filename = IdToFilename(id, index);
@@ -300,7 +300,7 @@ DiskCache::Entry* DiskCache::GetOrCreateEntry(const std::string& id,
   if (it != map_.end())
     return &it->second;
   if (!create)
-    return NULL;
+    return nullptr;
   Entry e;
   e.lock_state = LS_UNLOCKED;
   e.accessors = 0;