Check if GeneratedCodeCacheContext is not null when using it

For Incognito mode (and other cases where code caches are disabled)
we do not create the GeneratedCodeCacheContext or the GeneratedCodeCache.
It is required to verify they are non-null before using them.

Bug: chromium:881792, chromium:881881
Change-Id: I9cf47ed45e88c2e4df1f4d0a499149893332c98a
Reviewed-on: https://chromium-review.googlesource.com/1215682Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589873}

content/browser/renderer_host/render_message_filter.cc

@@ -245,7 +245,8 @@ void RenderMessageFilter::DidGenerateCacheableMetadata(
         base::BindOnce(&RenderMessageFilter::DidGenerateCacheableMetadataOnUI,
                        this, url, expected_response_time, data));
   } else {
-    if (!generated_code_cache_context_->generated_code_cache())
+    if (!generated_code_cache_context_ ||
+        !generated_code_cache_context_->generated_code_cache())
       return;
 
     base::Optional<url::Origin> requesting_origin =
@@ -260,7 +261,8 @@ void RenderMessageFilter::DidGenerateCacheableMetadata(
 
 void RenderMessageFilter::FetchCachedCode(const GURL& url,
                                           FetchCachedCodeCallback callback) {
-  if (!generated_code_cache_context_->generated_code_cache()) {
+  if (!generated_code_cache_context_ ||
+      !generated_code_cache_context_->generated_code_cache()) {
     std::move(callback).Run(base::Time(), std::vector<uint8_t>());
     return;
   }
@@ -290,7 +292,8 @@ void RenderMessageFilter::OnReceiveCachedCode(
 }
 
 void RenderMessageFilter::ClearCodeCacheEntry(const GURL& url) {
-  if (!generated_code_cache_context_->generated_code_cache())
+  if (!generated_code_cache_context_ ||
+      !generated_code_cache_context_->generated_code_cache())
     return;
 
   base::Optional<url::Origin> requesting_origin =