Bug 1443587 - part 1 - make EventInfo string getters return dependent strings; r=chutten

These methods are returning nsCString wrappers for static char arrays;
we only need to return nsDependentCStrings, rather than allocating and
copying entirely new nsCString objects.

toolkit/components/telemetry/EventInfo.h

@@ -32,9 +32,9 @@ struct CommonEventInfo {
   mozilla::Telemetry::Common::RecordedProcessType record_in_processes;
 
   // Convenience functions for accessing event strings.
-  const nsCString expiration_version() const;
-  const nsCString category() const;
-  const nsCString extra_key(uint32_t index) const;
+  const nsDependentCString expiration_version() const;
+  const nsDependentCString category() const;
+  const nsDependentCString extra_key(uint32_t index) const;
 };
 
 struct EventInfo {
@@ -45,8 +45,8 @@ struct EventInfo {
   uint32_t method_offset;
   uint32_t object_offset;
 
-  const nsCString method() const;
-  const nsCString object() const;
+  const nsDependentCString method() const;
+  const nsDependentCString object() const;
 };
 
 } // namespace

toolkit/components/telemetry/TelemetryEvent.cpp

@@ -199,37 +199,37 @@ private:
 };
 
 // Implements the methods for EventInfo.
-const nsCString
+const nsDependentCString
 EventInfo::method() const
 {
-  return nsCString(&gEventsStringTable[this->method_offset]);
+  return nsDependentCString(&gEventsStringTable[this->method_offset]);
 }
 
-const nsCString
+const nsDependentCString
 EventInfo::object() const
 {
-  return nsCString(&gEventsStringTable[this->object_offset]);
+  return nsDependentCString(&gEventsStringTable[this->object_offset]);
 }
 
 // Implements the methods for CommonEventInfo.
-const nsCString
+const nsDependentCString
 CommonEventInfo::category() const
 {
-  return nsCString(&gEventsStringTable[this->category_offset]);
+  return nsDependentCString(&gEventsStringTable[this->category_offset]);
 }
 
-const nsCString
+const nsDependentCString
 CommonEventInfo::expiration_version() const
 {
-  return nsCString(&gEventsStringTable[this->expiration_version_offset]);
+  return nsDependentCString(&gEventsStringTable[this->expiration_version_offset]);
 }
 
-const nsCString
+const nsDependentCString
 CommonEventInfo::extra_key(uint32_t index) const
 {
   MOZ_ASSERT(index < this->extra_count);
   uint32_t key_index = gExtraKeysTable[this->extra_index + index];
-  return nsCString(&gEventsStringTable[key_index]);
+  return nsDependentCString(&gEventsStringTable[key_index]);
 }
 
 // Implementation for the EventRecord class.