Adding DiscardSystemPages to gin/v8_platform.cc

Bug: chromium:897074
Change-Id: Id9dd6a634fce75e39f1d01f832337ff8702e042c
Reviewed-on: https://chromium-review.googlesource.com/c/1293452Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601889}

gin/v8_platform.cc

@@ -249,6 +249,11 @@ class PageAllocator : public v8::PageAllocator {
                                         GetPageConfig(permissions));
     }
   }
+
+  bool DiscardSystemPages(void* address, size_t size) override {
+    base::DiscardSystemPages(address, size);
+    return true;
+  }
 };
 
 base::LazyInstance<PageAllocator>::Leaky g_page_allocator =