Add throttling to permission reporter

chrome/browser/safe_browsing/permission_reporter.h

Index: chrome/browser/safe_browsing/permission_reporter.h
diff --git a/chrome/browser/safe_browsing/permission_reporter.h b/chrome/browser/safe_browsing/permission_reporter.h
index 523de8e57057aa67d749f31333c690896448f132..83521d5bd640b65d05a7371b1b806cee5f056ebc 100644
--- a/chrome/browser/safe_browsing/permission_reporter.h
+++ b/chrome/browser/safe_browsing/permission_reporter.h
@@ -5,8 +5,11 @@
 #ifndef CHROME_BROWSER_SAFE_BROWSING_PERMISSION_REPORTER_H_
 #define CHROME_BROWSER_SAFE_BROWSING_PERMISSION_REPORTER_H_
 
+#include <queue>
 #include <string>
+#include <unordered_map>
 
+#include "base/time/time.h"
 #include "chrome/browser/permissions/permission_uma_util.h"
 #include "url/gurl.h"
 
@@ -17,6 +20,18 @@ class URLRequestContext;
 
 namespace safe_browsing {
 
+struct PermissionAndOrigin {
+  bool operator==(const PermissionAndOrigin& other) const;
+
+  content::PermissionType permission;
+  GURL origin;
+};
+
+struct PermissionAndOriginHash {
+  std::size_t operator()(
+      const PermissionAndOrigin& permission_and_origin) const;
+};
+
 // Provides functionality for building and serializing reports about permissions
 // to a report collection server.
 class PermissionReporter {
@@ -55,8 +70,18 @@ class PermissionReporter {
                           PermissionAction action,
                           std::string* output);
 
+  // Returns true if the number of reports sent in the last one minute per
+  // origin per permission is less than |kMaximumReportPerOriginPerPermission|,
+  // otherwise false.

[raymes, 2016/06/27 06:26:56]

nit: probably don't reference the constant here, since it's not defined in this
file - just say "is under a threshold" or something similar

[stefanocs, 2016/06/27 07:34:57]

Done.

+  bool IsAllowedToSend(content::PermissionType permission, const GURL& origin);
+
   std::unique_ptr<net::ReportSender> permission_report_sender_;
 
+  std::unordered_map<PermissionAndOrigin,
+                     std::queue<base::Time>,

[raymes, 2016/06/27 06:26:56]

I think perhaps we can simplify this a little bit. What if we store a timestamp
whenever a send occurs and then just count the number of sends that happen since
that timestamp. If the current time is more than 1 min after the timestamp we
can reset everything.

Then we could just store:

base::Time send_timestamp_;
std::unordered_map<PermissionAndOrigin, int> send_counts_;

[stefanocs, 2016/06/27 07:34:57]

I think it would be possible to have more than five reports in window of one
minute like if reports are sent at 0, 57, 58, 59, 60, (reset here),  61, 62, 63,
64, 65 (in sec). While it still does prevents spamming to the server, it does
not exactly follow the definition, is that ok?

+                     PermissionAndOriginHash>
+      sent_histories;
+
   DISALLOW_COPY_AND_ASSIGN(PermissionReporter);
 };