Modify data_reduction_proxy_header to support tamper detection logic.

components/data_reduction_proxy/common/data_reduction_proxy_headers.cc

Index: components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
diff --git a/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc b/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
index e48afc366876e3aed082e133548044b45713a1f2..75142b0376c1f40d291448296c964a1809de977e 100644
--- a/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
+++ b/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
@@ -23,6 +23,27 @@ namespace data_reduction_proxy {
 const char* kDataReductionProxyViaValues[] = {"Chrome-Compression-Proxy",
                                               "Chrome Compression Proxy"};
 
+bool GetDataReductionProxyActionValue(
+    const net::HttpResponseHeaders* headers,
+    const std::string& action_prefix,
+    std::string* action_value) {
+  void* iter = NULL;
+  std::string value;
+  std::string name = "chrome-proxy";

[bolian, 2014/07/14 19:23:58]

inline this in the func call.  (Don't we have constant for this yet?)

[xingx, 2014/07/14 21:37:16]

Acknowledged.

[bolian, 2014/07/14 22:42:43]

?

[xingx, 2014/07/14 22:51:08]

Copied code from below.

+
+  while (headers->EnumerateHeader(&iter, name, &value)) {
+    if (value.size() > action_prefix.size()) {

[xingx, 2014/07/14 21:37:16]

Done.

It should be ">=" to get the empty value, but right now, at least action_prefix
+ "=", so it needs to be ">"

+      if (LowerCaseEqualsASCII(value.begin(),
+                               value.begin() + action_prefix.size(),
+                               action_prefix.c_str())) {
+        *action_value = value.substr(action_prefix.size());

[bengr, 2014/07/14 18:27:13]

Before the loop, either DCHECK that action_value is not NULL, or, if you allow
NULL, only write to action_value if not NULL.

[xingx, 2014/07/14 21:37:16]

Done.

+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 bool GetDataReductionProxyBypassDuration(
     const net::HttpResponseHeaders* headers,
     const std::string& action_prefix,