#122081 Universalchardet leaks memory

The fix for the nsCharSetProber class declaration, plus fix for
nsUniversalDetector methods, which may cause another leak when the object is
reused after Reset().

Patch proposed by Takayuki Tamura
r=shanjian, sr/a=brendan

extensions/universalchardet/src/base/nsCharSetProber.h

@@ -50,6 +50,7 @@ typedef enum {
 
 class nsCharSetProber {
 public:
+  virtual ~nsCharSetProber() {};
   virtual const char* GetCharSetName() = 0;
   virtual nsProbingState HandleData(const char* aBuf, PRUint32 aLen) = 0;
   virtual nsProbingState GetState(void) = 0;

extensions/universalchardet/src/base/nsUniversalDetector.cpp

@@ -89,7 +89,6 @@ nsUniversalDetector::Reset()
   mDone = PR_FALSE;
   mBestGuess = -1;   //illegal value as signal
   mInTag = PR_FALSE;
-  mEscCharSetProber = nsnull;
 
   mStart = PR_TRUE;
   mDetectedCharset = nsnull;
@@ -148,8 +147,10 @@ void nsUniversalDetector::HandleData(const char* aBuf, PRUint32 aLen)
         mInputState = eHighbyte;
 
         //kill mEscCharSetProber if it is active
-        if (mEscCharSetProber)
+        if (mEscCharSetProber) {
           delete mEscCharSetProber;
+          mEscCharSetProber = nsnull;
+        }
 
         //start multibyte and singlebyte charset prober
         if (nsnull == mCharSetProbers[0])