Fixing some warnings in xpcom. Bug 118377, r=hwaara, sr=shaver.

xpcom/ds/nsObserverList.cpp

@@ -102,7 +102,7 @@ nsObserverList::AddObserver(nsIObserver* anObserver, PRBool ownsWeak)
 nsresult
 nsObserverList::RemoveObserver(nsIObserver* anObserver)
 {
-	PRBool removed;
+    PRBool removed = PR_FALSE;
     
     NS_ENSURE_ARG(anObserver);
 

xpcom/io/nsAppFileLocationProvider.cpp

@@ -407,7 +407,7 @@ class nsAppDirectoryEnumerator : public nsISimpleEnumerator
         return *result ? NS_OK : NS_ERROR_FAILURE;
     }
 
-    ~nsAppDirectoryEnumerator() // I don't expect to be subclassed
+    virtual ~nsAppDirectoryEnumerator()
     {
     }
 

xpcom/io/nsPipe2.cpp

@@ -99,6 +99,7 @@ public:
         }
 
         nsPipeInputStream() : mReaderRefCnt(0), mBlocking(PR_TRUE) {}
+        virtual ~nsPipeInputStream() { }
         nsresult Fill();
 
     protected:
@@ -134,6 +135,7 @@ public:
         }
 
         nsPipeOutputStream() : mWriterRefCnt(0), mBlocking(PR_TRUE) {}
+        virtual ~nsPipeOutputStream() { }
 
     protected:
         nsrefcnt        mWriterRefCnt; // separate refcnt so that we know when to close the producer

xpcom/reflect/xptinfo/src/xptiZipLoader.cpp

@@ -109,7 +109,7 @@ xptiZipLoader::EnumerateZipEntries(nsILocalFile* file,
 
     do
     {
-        PRBool result;
+        PRBool result = PR_FALSE;
         int index = 0;
         PRBool hasMore;