Fix up strings Sky passes to base/trace_event

sky/engine/core/frame/Tracing.cpp

Index: sky/engine/core/frame/Tracing.cpp
diff --git a/sky/engine/core/frame/Tracing.cpp b/sky/engine/core/frame/Tracing.cpp
index 3359da2abb77fc51d02999922bd1cf9c567341a1..f05932615f1b50b9280f15b65d2707e78ce6dab1 100644
--- a/sky/engine/core/frame/Tracing.cpp
+++ b/sky/engine/core/frame/Tracing.cpp
@@ -21,13 +21,17 @@ Tracing::~Tracing()
 void Tracing::begin(const String& name)
 {
     StringUTF8Adaptor utf8(name);
-    TRACE_EVENT_COPY_BEGIN0("script", utf8.data());
+    // TRACE_EVENT_COPY_BEGIN0 needs a c-style null-terminated string.

[jamesr, 2015/04/29 00:12:46]

in particular, StringUTF8Adapter::data() doesn't return a pointer to a
null-terminated buffer

+    CString cstring(utf8.data(), utf8.length());

[jamesr, 2015/04/29 00:12:46]

this could be std::string as well. I figured CString is probably preferred here

+    TRACE_EVENT_COPY_BEGIN0("script", cstring.data());
 }
 
 void Tracing::end(const String& name)
 {
     StringUTF8Adaptor utf8(name);
-    TRACE_EVENT_COPY_END0("script", utf8.data());
+    // TRACE_EVENT_COPY_END0 needs a c-style null-terminated string.
+    CString cstring(utf8.data(), utf8.length());
+    TRACE_EVENT_COPY_END0("script", cstring.data());
 }
 
 } // namespace blink