MacKeyboard: Don't generate keypress for non-printable char

base/mac/mac_util.mm

Index: base/mac/mac_util.mm
diff --git a/base/mac/mac_util.mm b/base/mac/mac_util.mm
index 647faf3866f0d52d982e532e8cd2568ef12efce5..ccb694878ba8693a0abaf853899f72f55531d8e4 100644
--- a/base/mac/mac_util.mm
+++ b/base/mac/mac_util.mm
@@ -402,6 +402,24 @@ bool RemoveQuarantineAttribute(const FilePath& file_path) {
   return status == 0 || errno == ENOATTR;
 }
 
+bool CharacterIsPrintable(unichar c) {
+  switch (c) {
+  case 0xf728:  // Delete
+    return false;
+  }
+  return true;
+}
+
+bool StringIsPrintable(NSString* s) {
+  if (s.length == 0)
+    return true;
+  for (NSUInteger i = 0; i < s.length; ++i) {
+    if (CharacterIsPrintable([s characterAtIndex:i]))
+      return true;
+  }
+  return false;
+}
+
 namespace {
 
 // Returns the running system's Darwin major version. Don't call this, it's