Valgrind Mac: Restore a couple suppressions that are still active.

tools/valgrind/memcheck/suppressions_mac.txt

Index: tools/valgrind/memcheck/suppressions_mac.txt
diff --git a/tools/valgrind/memcheck/suppressions_mac.txt b/tools/valgrind/memcheck/suppressions_mac.txt
index c5e11d6e7c6352d7a4232a91f7b8549688358d14..66885a4f6ba8abd3968825a76738a7504c765ddb 100644
--- a/tools/valgrind/memcheck/suppressions_mac.txt
+++ b/tools/valgrind/memcheck/suppressions_mac.txt
@@ -94,6 +94,17 @@
    fun:__CFRunLoopRun
    ...
 }
+# Intentional leaks in AppKit, for an OS-level cache. Only appear on the first
+# run of each reboot.  See also issues 105525, 257276, 340847.
+{
+   bug_257276_b
+   Memcheck:Leak
+   fun:malloc_zone_malloc
+   ...
+   fun:setCursorFromBundle
+   fun:CoreCursorSet
+   fun:-[NSCursor set]
+}
 
 # 2. Intentional unit test errors, stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing.
@@ -162,6 +173,18 @@
    fun:_ZN19SkScalerContext_Mac13generateImageERK7SkGlyph
 }
 {
+   bug_173779
+   Memcheck:Uninitialized
+   ...
+   fun:img_data_lock
+   fun:CGSImageDataLock
+   fun:ripc_AcquireImage
+   fun:ripc_DrawImage*
+   fun:CGContextDrawImage*
+   ...
+   fun:_ZN11CUIRenderer4DrawE6CGRectP9CGContextPK14__CFDictionaryPS5_
+}
+{
   bug_340726
   Memcheck:Leak
   fun:_Znw*