Fixing possible read on URLRequest when there is no more data.

chrome/browser/predictors/resource_prefetcher.cc

Index: chrome/browser/predictors/resource_prefetcher.cc
diff --git a/chrome/browser/predictors/resource_prefetcher.cc b/chrome/browser/predictors/resource_prefetcher.cc
index 44b1057c4165839429cda432b446087e27efc25b..1419ffc9561a29026a34d59765d7aaa2a24b11a1 100644
--- a/chrome/browser/predictors/resource_prefetcher.cc
+++ b/chrome/browser/predictors/resource_prefetcher.cc
@@ -169,17 +169,17 @@ void ResourcePrefetcher::ReadFullResponse(net::URLRequest* request) {
         kResourceBufferSizeBytes));
     status = request->Read(buffer, kResourceBufferSizeBytes, &bytes_read);
 
-    if (status) {
-      if (request->status().error()) {
-        FinishRequest(request, Request::PREFETCH_STATUS_FAILED);
-        return;
-      } else if (bytes_read == 0) {
-        if (request->was_cached())
-          FinishRequest(request, Request::PREFETCH_STATUS_FROM_CACHE);
-        else
-          FinishRequest(request, Request::PREFETCH_STATUS_FROM_NETWORK);
-        return;
-      }
+    if (request->status().error()) {

[rvargas (doing something else), 2013/01/04 02:02:40]

The contract is not to inspect status() regardless of the return value. The
first thing to check is the return value of the function (as the old code does).

[Shishir, 2013/01/04 02:21:14]

From the comment on the Read function:
// If a read error occurs, Read returns false and the request->status
// will be set to an error.

So if read returns false, its either because its in async mode or there is an
error. Earlier we were checking error when status was true which would never
happen. This condition will rightly bail out in the case where there is an error
bit set and the read returns false.

+      FinishRequest(request, Request::PREFETCH_STATUS_FAILED);
+      return;
+    }
+
+    if (status && bytes_read == 0) {  // When bytes_read == 0, no more data.
+      if (request->was_cached())
+        FinishRequest(request, Request::PREFETCH_STATUS_FROM_CACHE);
+      else
+        FinishRequest(request, Request::PREFETCH_STATUS_FROM_NETWORK);
+      return;
     }
   }
 }
@@ -223,6 +223,15 @@ void ResourcePrefetcher::OnReadCompleted(net::URLRequest* request,
     return;
   }
 
+  // If the bytes_read is == 0, there is no more data to read.
+  if (bytes_read == 0) {
+    if (request->was_cached())
+      FinishRequest(request, Request::PREFETCH_STATUS_FROM_CACHE);
+    else
+      FinishRequest(request, Request::PREFETCH_STATUS_FROM_NETWORK);
+    return;
+  }
+
   ReadFullResponse(request);
 }