Avoid copying and strlen(3) in the FindClass path.

Change-Id: I789f3c883596d1852a2c1954ce7a207e6f937117
diff --git a/src/common_test.h b/src/common_test.h
index 5093976..396cda5 100644
--- a/src/common_test.h
+++ b/src/common_test.h
@@ -331,7 +331,7 @@
 
   void CompileClass(const ClassLoader* class_loader, const char* class_name) {
     std::string class_descriptor(DotToDescriptor(class_name));
-    Class* klass = class_linker_->FindClass(class_descriptor, class_loader);
+    Class* klass = class_linker_->FindClass(class_descriptor.c_str(), class_loader);
     CHECK(klass != NULL) << "Class not found " << class_name;
     for (size_t i = 0; i < klass->NumDirectMethods(); i++) {
       CompileMethod(klass->GetDirectMethod(i));
@@ -354,7 +354,7 @@
                            const char* method_name,
                            const char* signature) {
     std::string class_descriptor(DotToDescriptor(class_name));
-    Class* klass = class_linker_->FindClass(class_descriptor, class_loader);
+    Class* klass = class_linker_->FindClass(class_descriptor.c_str(), class_loader);
     CHECK(klass != NULL) << "Class not found " << class_name;
     Method* method = klass->FindDirectMethod(method_name, signature);
     CHECK(method != NULL) << "Direct method not found: "
@@ -367,7 +367,7 @@
                             const char* method_name,
                             const char* signature) {
     std::string class_descriptor(DotToDescriptor(class_name));
-    Class* klass = class_linker_->FindClass(class_descriptor, class_loader);
+    Class* klass = class_linker_->FindClass(class_descriptor.c_str(), class_loader);
     CHECK(klass != NULL) << "Class not found " << class_name;
     Method* method = klass->FindVirtualMethod(method_name, signature);
     CHECK(method != NULL) << "Virtual method not found: "