[Sheriff] Tentative fix for ios_simulator build issues

Our guess is that OS_MACOSX is true for ios, but the mojom file
here uses is_mac (which isn't true for ios). So the guards on the
file are wrong. However the file has existed for months, so it is
not clear why it suddenly failed now - hence tentative!

Bug: None
Change-Id: I721db80c8360fbe2c3461dce28afba9a61344fc5

TBR=ccameron@chromium.org
NOTREECHECKS=true
NOTRY=true

Change-Id: I721db80c8360fbe2c3461dce28afba9a61344fc5
Reviewed-on: https://chromium-review.googlesource.com/c/1258048
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Reviewed-by: Stephen McGruer <smcgruer@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595964}

ui/base/mojo/clipboard_host.h

@@ -58,7 +58,7 @@ class ClipboardHost : public mojom::ClipboardHost {
   void WriteBitmap(const SkBitmap& bitmap) override;
   void WriteData(const std::string& type, const std::string& data) override;
   void CommitWrite(ClipboardType type) override;
-#if defined(OS_MACOSX)
+#if defined(OS_MACOSX) && !defined(OS_IOS)
   void WriteStringToFindPboard(const base::string16& text) override;
 #endif