Avoid crashing the browser on truncated reads from the cache backend

net/http/http_cache_transaction.cc

Index: net/http/http_cache_transaction.cc
diff --git a/net/http/http_cache_transaction.cc b/net/http/http_cache_transaction.cc
index 07fa4dbacc4dbb68763c70cfde3c639a809e6677..090e8f25783348beaa5675555556fac47248ec27 100644
--- a/net/http/http_cache_transaction.cc
+++ b/net/http/http_cache_transaction.cc
@@ -1385,6 +1385,17 @@ int HttpCache::Transaction::DoCacheReadResponse() {
   next_state_ = STATE_CACHE_READ_RESPONSE_COMPLETE;
 
   io_buf_len_ = entry_->disk_entry->GetDataSize(kResponseInfoIndex);
+  if (io_buf_len_ > 0) {
+    UMA_HISTOGRAM_BOOLEAN("HttpCache.HeaderTruncated", false);
+  } else {
+    UMA_HISTOGRAM_BOOLEAN("HttpCache.HeaderTruncated", true);
+    DLOG(WARNING) << "Truncated cache entry header encountered";
+    mode_ = NONE;
+    if (partial_.get())
+      partial_->RestoreHeaders(&custom_request_->extra_headers);
+    next_state_ = STATE_SEND_REQUEST;
+    return OK;
+  }
   read_buf_ = new IOBuffer(io_buf_len_);
 
   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_READ_INFO);
@@ -1482,8 +1493,19 @@ int HttpCache::Transaction::DoCacheReadMetadata() {
   DCHECK(!response_.metadata);
   next_state_ = STATE_CACHE_READ_METADATA_COMPLETE;
 
-  response_.metadata =
-      new IOBufferWithSize(entry_->disk_entry->GetDataSize(kMetadataIndex));
+  int32 data_size = entry_->disk_entry->GetDataSize(kMetadataIndex);
+  if (data_size > 0) {
+    UMA_HISTOGRAM_BOOLEAN("HttpCache.MetadataTruncated", false);
+  } else {
+    UMA_HISTOGRAM_BOOLEAN("HttpCache.MetadataTruncated", true);
+    DLOG(WARNING) << "Truncated cache entry metadata encountered";
+    mode_ = NONE;
+    if (partial_.get())
+      partial_->RestoreHeaders(&custom_request_->extra_headers);
+    next_state_ = STATE_SEND_REQUEST;
+    return OK;
+  }
+  response_.metadata = new IOBufferWithSize(data_size);
 
   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_READ_INFO);
   ReportCacheActionStart();