Support requesting subsets of host permissions using the permissions API.

extensions/common/url_pattern_set.h

Index: extensions/common/url_pattern_set.h
diff --git a/extensions/common/url_pattern_set.h b/extensions/common/url_pattern_set.h
index 2f7113973835ffe4346b00ac199cc1723d07cd65..803abf51c79fb9fc57479fb2b848572ecc11b7a5 100644
--- a/extensions/common/url_pattern_set.h
+++ b/extensions/common/url_pattern_set.h
@@ -5,6 +5,7 @@
 #ifndef EXTENSIONS_COMMMON_URL_PATTERN_SET_H_
 #define EXTENSIONS_COMMMON_URL_PATTERN_SET_H_
 
+#include <ostream>
 #include <set>
 
 #include "base/memory/scoped_ptr.h"
@@ -69,8 +70,21 @@ class URLPatternSet {
   void ClearPatterns();
 
   // Returns true if the permission |set| is a subset of this.
+  //
+  // This is equality based, so {<all_urls>} is not considered to contain
+  // {google.com}. For that, use Encompasses.

[Matt Perry, 2013/02/12 01:14:47]

This is a strange distinction. Why not just fix Contains to do what Encompasses
does? Are you worried that there are other uses of Contains that do not want to
match <all_urls>?

[not at google - send to devlin, 2013/02/12 01:49:36]

Yeah, it is strange. I had it like you said - just make Contains be smart - but
it introduced a problem (though I can't think of it right now...).

Hm well here is one, maybe. There are a lot of set-idiom-methods on these
objects (notably difference/intersection/union) which work just off the actual
patterns that have been added, and it may be surprising that Contains (obviously
also a set-idiom-method) behaves differently. Not convinced that's a big deal.

Actually perhaps the problem was that I was worried about all the corner cases,
and it seemed more manageable this way, specifically permissions.remove - I
wanted to make sure only actually-added permissions could be removed - but later
I saw that the function basically always returns "true" so it was moot.

I'll just change Contains and see what happens.

   bool Contains(const URLPatternSet& set) const;
 
+  // Returns true if any pattern in this set encompasses |pattern|.
+  //
+  // This is more inclusive than Contains: while {all_urls} is not considered
+  // to contain {google.com}, it does encompass it.
+  bool EncompassesPattern(const URLPattern& pattern) const;
+
+  // Returns true if every pattern in |other| is encompassed by some pattern
+  // in this set.
+  bool Encompasses(const URLPatternSet& other) const;
+
   // Test if the extent contains a URL.
   bool MatchesURL(const GURL& url) const;
 
@@ -96,6 +110,8 @@ class URLPatternSet {
   std::set<URLPattern> patterns_;
 };
 
+std::ostream& operator<<(std::ostream& out, const URLPatternSet& set);
+
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMMON_URL_PATTERN_SET_H_