Fix a crash in the extension system when sending response back to extension with no results. Also found an UMR causing DCHECKs to hit repeatedly (in AsyncExtensionFunction::SetArgs).

BUG=None
TEST=Basically, use any extension that calls an API function that returns no results (such as PageAction) and Chrome should not crash.
Review URL: http://codereview.chromium.org/114033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@16325 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 7 insertions, 4 deletions

diff --git a/chrome/browser/extensions/extension_function.cc b/chrome/browser/extensions/extension_function.cc
index f74fdb9..a846d96 100644
--- a/chrome/browser/extensions/extension_function.cc
+++ b/chrome/browser/extensions/extension_function.cc
@@ -10,7 +10,7 @@
 #include "chrome/browser/extensions/extension_function_dispatcher.h"
 
 void AsyncExtensionFunction::SetArgs(const std::string& args) {
-  DCHECK(!args_);  // should only be called once
+  DCHECK(!args_);  // Should only be called once.
   if (!args.empty()) {
     JSONReader reader;
     args_ = reader.JsonToValue(args, false, false);
@@ -26,7 +26,9 @@ void AsyncExtensionFunction::SetArgs(const std::string& args) {
 
 const std::string AsyncExtensionFunction::GetResult() {
   std::string json;
-  JSONWriter::Write(result_.get(), false, &json);
+  // Some functions might not need to return any results.
+  if (result_.get())
+    JSONWriter::Write(result_.get(), false, &json);
   return json;
 }
 
diff --git a/chrome/browser/extensions/extension_function.h b/chrome/browser/extensions/extension_function.h
index cbe85b9..5d0ddb0 100644
--- a/chrome/browser/extensions/extension_function.h
+++ b/chrome/browser/extensions/extension_function.h
@@ -28,6 +28,7 @@ class Profile;
 class ExtensionFunction {
  public:
   ExtensionFunction() : request_id_(-1), has_callback_(false) {}
+  virtual ~ExtensionFunction() {}
 
   // Specifies the name of the function.
   virtual void SetName(const std::string& name) { }
@@ -79,7 +80,7 @@ class ExtensionFunction {
 // parsing JSON (and instead uses custom serialization of Value objects).
 class AsyncExtensionFunction : public ExtensionFunction {
  public:
-  AsyncExtensionFunction() : bad_message_(false) {}
+  AsyncExtensionFunction() : args_(NULL), bad_message_(false) {}
   virtual ~AsyncExtensionFunction() {}
 
   virtual void SetArgs(const std::string& args);
@@ -94,7 +95,7 @@ class AsyncExtensionFunction : public ExtensionFunction {
 
   Profile* profile();
 
-  // The arguments to the API. Only non-null if argument were specfied.
+  // The arguments to the API. Only non-null if argument were specified.
   Value* args_;
 
   // The result of the API. This should be populated by the derived class before