[Courgette] Refactor BSDiff namespaces and bsdiff::search() interface.

courgette/third_party/bsdiff/bsdiff_apply.cc

Index: courgette/third_party/bsdiff/bsdiff_apply.cc
diff --git a/courgette/third_party/bsdiff/bsdiff_apply.cc b/courgette/third_party/bsdiff/bsdiff_apply.cc
index e0d99ad1c5d48e51516f725a06745c7363e9c866..9d96c62a77d4175f6beb42577ecb46d44512ade1 100644
--- a/courgette/third_party/bsdiff/bsdiff_apply.cc
+++ b/courgette/third_party/bsdiff/bsdiff_apply.cc
@@ -44,7 +44,17 @@
 #include "courgette/crc.h"
 #include "courgette/streams.h"
 
-namespace courgette {
+namespace {
+
+using courgette::CalculateCrc;
+using courgette::SinkStream;
+using courgette::SinkStreamSet;
+using courgette::SourceStream;
+using courgette::SourceStreamSet;
+
+}  // namespace
+
+namespace bsdiff {
 
 BSDiffStatus MBS_ReadHeader(SourceStream* stream, MBSPatchHeader* header) {
   if (!stream->Read(header->tag, sizeof(header->tag)))
@@ -215,4 +225,4 @@ BSDiffStatus ApplyBinaryPatch(const base::FilePath& old_file_path,
   return OK;
 }
 
-}  // namespace
+}  // namespace bsdiff