Bug 1494127 - Fix trivial calls to do_QueryInterface that return an nsresult r=smaug

Calls to do_QueryInterface to a base class can be replaced by a static
cast, which is faster.

Differential Revision: https://phabricator.services.mozilla.com/D7224

--HG--
extra : moz-landing-system : lando

extensions/permissions/nsContentBlocker.cpp

@@ -123,8 +123,7 @@ nsContentBlocker::Init()
   // The branch is not a copy of the prefservice, but a new object, because
   // it is a non-default branch. Adding obeservers to it will only work if
   // we make sure that the object doesn't die. So, keep a reference to it.
-  mPrefBranchInternal = do_QueryInterface(prefBranch, &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
+  mPrefBranchInternal = prefBranch;
 
   rv = mPrefBranchInternal->AddObserver("", this, true);
   PrefChanged(prefBranch, nullptr);

image/decoders/icon/nsIconURI.cpp

@@ -512,13 +512,9 @@ nsMozIconURI::SchemeIs(const char* aScheme, bool* aEquals)
 nsresult
 nsMozIconURI::Clone(nsIURI** result)
 {
-  nsresult rv;
   nsCOMPtr<nsIURL> newIconURL;
   if (mIconURL) {
-    newIconURL = do_QueryInterface(mIconURL, &rv);
-    if (NS_FAILED(rv)) {
-      return rv;
-    }
+    newIconURL = mIconURL;
   }
 
   RefPtr<nsMozIconURI> uri = new nsMozIconURI();

js/xpconnect/src/XPCShellImpl.cpp

@@ -1224,7 +1224,7 @@ XRE_XPCShellMain(int argc, char** argv, char** envp,
             nsCOMPtr<nsIFile> dir;
             rv = XRE_GetFileFromPath(argv[2], getter_AddRefs(dir));
             if (NS_SUCCEEDED(rv)) {
-                appDir = do_QueryInterface(dir, &rv);
+                appDir = dir;
                 dirprovider.SetAppDir(appDir);
             }
             if (NS_FAILED(rv)) {

modules/libjar/zipwriter/nsZipDataStream.cpp

@@ -51,8 +51,7 @@ nsresult nsZipDataStream::Init(nsZipWriter *aWriter,
                                          nullptr);
         NS_ENSURE_SUCCESS(rv, rv);
 
-        mOutput = do_QueryInterface(converter, &rv);
-        NS_ENSURE_SUCCESS(rv, rv);
+        mOutput = converter;
     }
     else {
         mHeader->mMethod = ZIP_METHOD_STORE;

netwerk/base/nsStreamListenerTee.cpp

@@ -85,8 +85,7 @@ nsStreamListenerTee::OnDataAvailable(nsIRequest *request,
         rv = mInputTee->SetSource(input);
         if (NS_FAILED(rv)) return rv;
 
-        tee = do_QueryInterface(mInputTee, &rv);
-        if (NS_FAILED(rv)) return rv;
+        tee = mInputTee;
     }
 
     return mListener->OnDataAvailable(request, context, tee, offset, count);

netwerk/cache/nsCacheService.cpp

@@ -746,8 +746,9 @@ nsCacheProfilePrefObserver::ReadPrefs(nsIPrefBranch* branch)
             rv = NS_GetSpecialDirectory(NS_XPCOM_CURRENT_PROCESS_DIR,
                                         getter_AddRefs(directory));
         }
-        if (directory)
-            mDiskCacheParentDirectory = do_QueryInterface(directory, &rv);
+        if (directory) {
+            mDiskCacheParentDirectory = directory;
+        }
     }
     if (mDiskCacheParentDirectory) {
         bool firstSmartSizeRun;
@@ -816,8 +817,9 @@ nsCacheProfilePrefObserver::ReadPrefs(nsIPrefBranch* branch)
                                         getter_AddRefs(directory));
         }
 #endif
-        if (directory)
-            mOfflineCacheParentDirectory = do_QueryInterface(directory, &rv);
+        if (directory) {
+            mOfflineCacheParentDirectory = directory;
+        }
     }
 
     // read memory cache device prefs

netwerk/streamconv/converters/nsMultiMixedConv.cpp

@@ -996,10 +996,7 @@ nsMultiMixedConv::SendData()
     if (NS_FAILED(rv))
         return rv;
 
-    nsCOMPtr<nsIInputStream> inStream(do_QueryInterface(ss, &rv));
-    if (NS_FAILED(rv)) return rv;
-
-    return mPartChannel->SendOnDataAvailable(mContext, inStream, offset, mRawDataLength);
+    return mPartChannel->SendOnDataAvailable(mContext, ss, offset, mRawDataLength);
 }
 
 void

netwerk/streamconv/nsStreamConverterService.cpp

@@ -499,18 +499,12 @@ nsStreamConverterService::AsyncConvertData(const char *aFromType,
                 return rv;
             }
 
-            nsCOMPtr<nsIStreamListener> chainListener(do_QueryInterface(converter, &rv));
-            if (NS_FAILED(rv)) {
-                delete converterChain;
-                return rv;
-            }
-
             // the last iteration of this loop will result in finalListener
             // pointing to the converter that "starts" the conversion chain.
             // this converter's "from" type is the original "from" type. Prior
             // to the last iteration, finalListener will continuously be wedged
             // into the next listener in the chain, then be updated.
-            finalListener = chainListener;
+            finalListener = converter;
         }
         delete converterChain;
         // return the first listener in the chain.

toolkit/components/find/nsWebBrowserFind.cpp

@@ -139,11 +139,7 @@ nsWebBrowserFind::FindNext(bool* aResult)
   }
 
   // remember where we started
-  nsCOMPtr<nsIDocShellTreeItem> startingItem =
-    do_QueryInterface(searchFrame->GetDocShell(), &rv);
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
+  nsCOMPtr<nsIDocShellTreeItem> startingItem = searchFrame->GetDocShell();
 
   nsCOMPtr<nsIDocShellTreeItem> curItem;
 

toolkit/components/typeaheadfind/nsTypeAheadFind.cpp

@@ -562,8 +562,7 @@ nsTypeAheadFind::FindItNow(nsIPresShell *aPresShell, bool aIsLinksOnly,
           nsresult rv = fm->GetFocusedWindow(getter_AddRefs(focusedWindow));
           if (NS_SUCCEEDED(rv) && focusedWindow) {
             auto* fwPI = nsPIDOMWindowOuter::From(focusedWindow);
-            nsCOMPtr<nsIDocShellTreeItem> fwTreeItem
-              (do_QueryInterface(fwPI->GetDocShell(), &rv));
+            nsCOMPtr<nsIDocShellTreeItem> fwTreeItem(fwPI->GetDocShell());
             if (NS_SUCCEEDED(rv)) {
               nsCOMPtr<nsIDocShellTreeItem> fwRootTreeItem;
               rv = fwTreeItem->GetSameTypeRootTreeItem(getter_AddRefs(fwRootTreeItem));

toolkit/xre/nsUpdateDriver.cpp

@@ -175,8 +175,8 @@ GetFile(nsIFile* dir, const nsACString& name, nsCOMPtr<nsIFile>& result)
   if (NS_FAILED(rv))
     return false;
 
-  result = do_QueryInterface(file, &rv);
-  return NS_SUCCEEDED(rv);
+  result = file;
+  return true;
 }
 
 static bool

widget/nsBaseFilePicker.cpp

@@ -305,8 +305,8 @@ NS_IMETHODIMP nsBaseFilePicker::SetDisplayDirectory(nsIFile *aDirectory)
   nsresult rv = aDirectory->Clone(getter_AddRefs(directory));
   if (NS_FAILED(rv))
     return rv;
-  mDisplayDirectory = do_QueryInterface(directory, &rv);
-  return rv;
+  mDisplayDirectory = directory;
+  return NS_OK;
 }
 
 // Get the display directory