Fix `[Memory] Add OnCriticalMemoryPressure overload to v8::Platform.`

Fix 29bb707e

Compilation on GYP fails due to missing OnCriticalMemoryPressure
overload that accepts size_t parameter. In this case the compiler
complains about hiding virtual function.

This patch reintroduces the missing functions.

Bug: 
Change-Id: I493891f6908987a6f27c669a16f6c3772339333d
Reviewed-on: https://chromium-review.googlesource.com/844077Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Ivica Bogosavljevic <ivica.bogosavljevic@mips.com>
Cr-Commit-Position: refs/heads/master@{#50306}

test/cctest/cctest.h

@@ -688,6 +688,10 @@ class TestPlatform : public v8::Platform {
     old_platform_->OnCriticalMemoryPressure();
   }
 
+  bool OnCriticalMemoryPressure(size_t length) override {
+    return old_platform_->OnCriticalMemoryPressure(length);
+  }
+
   std::shared_ptr<v8::TaskRunner> GetForegroundTaskRunner(
       v8::Isolate* isolate) override {
     return old_platform_->GetForegroundTaskRunner(isolate);

test/cctest/test-allocation.cc

@@ -41,6 +41,11 @@ class AllocationPlatform : public TestPlatform {
 
   void OnCriticalMemoryPressure() override { oom_callback_called = true; }
 
+  bool OnCriticalMemoryPressure(size_t length) override {
+    oom_callback_called = true;
+    return true;
+  }
+
   static AllocationPlatform* current_platform;
   bool oom_callback_called = false;
 };