Fix handling of negative max_size in ::SimpleBackendImpl

Change-Id: I9d66473203995ff21d915b17cffa42c44f84a000
Reviewed-on: https://chromium-review.googlesource.com/598108
Commit-Queue: Maks Orlovich <morlovich@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491399}

net/disk_cache/backend_unittest.cc

@@ -3998,6 +3998,24 @@ TEST_F(DiskCacheBackendTest, SimpleCacheLateDoom) {
             simple_cache_impl_->index()->init_method());
 }
 
+TEST_F(DiskCacheBackendTest, SimpleCacheNegMaxSize) {
+  SetMaxSize(-1);
+  SetSimpleCacheMode();
+  InitCache();
+  // We don't know what it will pick, but it's limited to what
+  // disk_cache::PreferredCacheSize would return, scaled by the size experiment,
+  // which only goes as much as 2x. It definitely should not be MAX_UINT64.
+  EXPECT_NE(simple_cache_impl_->index()->max_size(),
+            std::numeric_limits<uint64_t>::max());
+
+  int max_default_size =
+      2 * disk_cache::PreferredCacheSize(std::numeric_limits<int32_t>::max());
+
+  ASSERT_GE(max_default_size, 0);
+  EXPECT_LT(simple_cache_impl_->index()->max_size(),
+            static_cast<unsigned>(max_default_size));
+}
+
 TEST_F(DiskCacheBackendTest, SimpleLastModified) {
   // Simple cache used to incorrectly set LastModified on entries based on
   // timestamp of the cache directory, and not the entries' file

net/disk_cache/simple/simple_backend_impl.cc

@@ -263,6 +263,10 @@ SimpleBackendImpl::SimpleBackendImpl(
                                  ? SimpleEntryImpl::OPTIMISTIC_OPERATIONS
                                  : SimpleEntryImpl::NON_OPTIMISTIC_OPERATIONS),
       net_log_(net_log) {
+  // Treat negative passed-in sizes same as SetMaxSize would here and in other
+  // backends, as default (if first call).
+  if (orig_max_size_ < 0)
+    orig_max_size_ = 0;
   MaybeHistogramFdLimit(cache_type_);
 }