Bug 1276567 - Fix -Wstring-conversion warnings in js/ directory. r=billm

js/ipc/WrapperAnswer.cpp:531:16 [-Wstring-conversion] implicit conversion turns string literal into bool: 'const char [12]' to 'bool'
js/src/jit/MIR.h:63:25 [-Wstring-conversion] implicit conversion turns string literal into bool: 'const char [26]' to 'bool'
js/src/jit/SharedIC.cpp:1648:21 [-Wstring-conversion] implicit conversion turns string literal into bool: 'const char [30]' to 'bool'
js/src/jsgc.cpp:7135:21 [-Wstring-conversion] implicit conversion turns string literal into bool: 'const char [59]' to 'bool'

js/ipc/WrapperAnswer.cpp

@@ -548,7 +548,8 @@ WrapperAnswer::RecvClassName(const ObjectId& objId, nsCString* name)
     RootedObject obj(cx, findObjectById(cx, objId));
     if (!obj) {
         // This is very unfortunate, but we have no choice.
-        return "<dead CPOW>";
+        *name = "<dead CPOW>";
+        return true;
     }
 
     LOG("%s.className()", ReceiverObj(objId));

js/src/jit/MIR.h

@@ -60,7 +60,7 @@ MIRType MIRTypeFromValue(const js::Value& vp)
           case JS_UNINITIALIZED_LEXICAL:
             return MIRType::MagicUninitializedLexical;
           default:
-            MOZ_ASSERT(!"Unexpected magic constant");
+            MOZ_ASSERT_UNREACHABLE("Unexpected magic constant");
         }
     }
     return MIRTypeFromValueType(vp.extractNonDoubleType());

js/src/jit/SharedIC.cpp

@@ -1645,7 +1645,7 @@ DoCompareFallback(JSContext* cx, void* payload, ICCompare_Fallback* stub_, Handl
             return false;
         break;
       default:
-        MOZ_ASSERT(!"Unhandled baseline compare op");
+        MOZ_ASSERT_UNREACHABLE("Unhandled baseline compare op");
         return false;
     }
 

js/src/jsgc.cpp

@@ -7122,7 +7122,7 @@ ArenaLists::normalizeBackgroundFinalizeState(AllocKind thingKind)
       case BFS_DONE:
         break;
       default:
-        MOZ_ASSERT(!"Background finalization in progress, but it should not be.");
+        MOZ_ASSERT_UNREACHABLE("Background finalization in progress, but it should not be.");
         break;
     }
 }