Use the tonic namespace for tonic + resulting build fixes

tonic/dart_converter.h

Index: tonic/dart_converter.h
diff --git a/tonic/dart_converter.h b/tonic/dart_converter.h
index f0387b28affe4a8906c94f806ff7d3cee21586bb..af6dcaf713d7193a937a642e7f59a7f40bf5122e 100644
--- a/tonic/dart_converter.h
+++ b/tonic/dart_converter.h
@@ -9,7 +9,7 @@
 
 #include "tonic/dart_state.h"
 
-namespace blink {
+namespace tonic {
 
 // DartConvert converts types back and forth from Sky to Dart. The template
 // parameter |T| determines what kind of type conversion to perform.
@@ -198,6 +198,6 @@ inline Dart_Handle ToDart(const char* val) {
   return Dart_NewStringFromCString(val);
 }
 
-}  // namespace blink
+}  // namespace tonic
 
 #endif  // SKY_ENGINE_TONIC_DART_CONVERTER_H_