Remove unneeded null checks in ImageBitmap.cpp.

`new` never returns nullptr per standard (in Chromium, we crash the process
on out-of-memory instead).

Also, in the first case, the image in the ImageBitmap is checked for nullness
right above, so that check isn't needed either.

Bug: 805881
Change-Id: Ieff5bdf15813bfb0f3087ec925f74ecacc77df7c
Reviewed-on: https://chromium-review.googlesource.com/887758Reviewed-by: Mohammad Reza Zakerinasab <zakerinasab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532503}

third_party/WebKit/Source/core/imagebitmap/ImageBitmap.cpp

@@ -821,15 +821,8 @@ void ImageBitmap::ResolvePromiseOnOriginalThread(
     return;
   }
   ImageBitmap* bitmap = new ImageBitmap(image);
-  if (bitmap && bitmap->BitmapImage())
-    bitmap->BitmapImage()->SetOriginClean(origin_clean);
-  if (bitmap && bitmap->BitmapImage()) {
-    resolver->Resolve(bitmap);
-  } else {
-    resolver->Reject(
-        ScriptValue(resolver->GetScriptState(),
-                    v8::Null(resolver->GetScriptState()->GetIsolate())));
-  }
+  bitmap->BitmapImage()->SetOriginClean(origin_clean);
+  resolver->Resolve(bitmap);
 }
 
 void ImageBitmap::RasterizeImageOnBackgroundThread(
@@ -887,11 +880,9 @@ ScriptPromise ImageBitmap::CreateAsync(ImageElementBase* image,
   // poremultiply_alpha.
   if (src_rect.IsEmpty()) {
     ImageBitmap* bitmap = new ImageBitmap(MakeBlankImage(parsed_options));
-    if (bitmap && bitmap->BitmapImage()) {
+    if (bitmap->BitmapImage()) {
       bitmap->BitmapImage()->SetOriginClean(
           !image->WouldTaintOrigin(document->GetSecurityOrigin()));
-    }
-    if (bitmap && bitmap->BitmapImage()) {
       resolver->Resolve(bitmap);
     } else {
       resolver->Reject(