Resolve some of clang's zero-as-null-pointer-constant warnings

src/hb-coretext.cc

@@ -210,7 +210,7 @@ create_ct_font (CGFontRef cg_font, CGFloat font_size)
       return ct_font;
   }
 
-  CFURLRef original_url = NULL;
+  CFURLRef original_url = nullptr;
 #if MAC_OS_X_VERSION_MIN_REQUIRED < 1060
   ATSFontRef atsFont;
   FSRef fsref;
@@ -240,7 +240,7 @@ create_ct_font (CGFontRef cg_font, CGFloat font_size)
        * system locations that we cannot access from the sandboxed renderer
        * process in Blink. This can be detected by the new file URL location
        * that the newly found font points to. */
-      CFURLRef new_url = NULL;
+      CFURLRef new_url = nullptr;
 #if MAC_OS_X_VERSION_MIN_REQUIRED < 1060
       atsFont = CTFontGetPlatformFont (new_ct_font, NULL);
       status = ATSFontGetFileReference (atsFont, &fsref);

src/hb-dsalgs.hh

@@ -49,7 +49,7 @@ hb_bsearch_r (const void *key, const void *base,
     else
       return (void *) p;
   }
-  return NULL;
+  return nullptr;
 }
 
 

src/hb-ot-os2-unicode-ranges.hh

@@ -237,7 +237,7 @@ hb_get_unicode_range_bit (hb_codepoint_t cp)
                                         sizeof (os2UnicodeRangesSorted) / sizeof(Range),
                                         sizeof(Range),
                                         _compare_range, nullptr);
-  if (range != NULL)
+  if (range != nullptr)
     return range->bit;
   return -1;
 }