Migrate to OS_MAC and OS_APPLE in pdf

Bug: 1105907
Change-Id: I27367f42ea8797dfac1add4d3568ed35fce558f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2324893Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792716}

pdf/pdfium/pdfium_engine.cc

@@ -277,7 +277,7 @@ bool IsLinkArea(PDFiumPage::Area area) {
 // button down events into a right button down events.
 MouseInputEvent NormalizeMouseEvent(const MouseInputEvent& event) {
   MouseInputEvent normalized_event = event;
-#if defined(OS_MACOSX)
+#if defined(OS_MAC)
   uint32_t modifiers = event.GetModifiers();
   if ((event.GetModifiers() & kInputEventModifierControlKey) &&
       event.GetButton() == InputEventMouseButtonType::kLeft &&
@@ -1584,7 +1584,7 @@ bool PDFiumEngine::OnKeyDown(const KeyboardInputEvent& event) {
     OnChar(synthesized);
   }
 
-#if !defined(OS_MACOSX)
+#if !defined(OS_MAC)
   // macOS doesn't have keyboard-triggered context menus.
   // Scroll focused annotation into view when context menu is invoked through
   // keyboard <Shift-F10>.

pdf/pdfium/pdfium_form_filler_unittest.cc

@@ -87,7 +87,7 @@ TEST_F(FormFillerTest, DoURIActionWithKeyboardModifier) {
         .Times(1);
   }
 
-#if defined(OS_MACOSX)
+#if defined(OS_MAC)
 #define modifier_key PP_INPUTEVENT_MODIFIER_METAKEY;
 #else
 #define modifier_key PP_INPUTEVENT_MODIFIER_CONTROLKEY