Move most of the implementation of AdjustAmountOfExternalMemory to v8.h

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index b1da55e2c5ee0d2cf566c976b95dde2e0396a27b..8984d92c75fc276bff432e35cd0570d7a40b3669 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -4215,7 +4215,8 @@ class V8_EXPORT Isolate {
    *   kept alive by JavaScript objects.
    * \returns the adjusted value.
    */
-  int64_t AdjustAmountOfExternalAllocatedMemory(int64_t change_in_bytes);
+  V8_INLINE int64_t
+      AdjustAmountOfExternalAllocatedMemory(int64_t change_in_bytes);
 
   /**
    * Returns heap profiler for this isolate. Will return NULL until the isolate
@@ -4418,6 +4419,7 @@ class V8_EXPORT Isolate {
   void SetObjectGroupId(internal::Object** object, UniqueId id);
   void SetReferenceFromGroup(UniqueId id, internal::Object** object);
   void SetReference(internal::Object** parent, internal::Object** child);
+  void CollectAllGarbage(const char* gc_reason);
 };
 
 class V8_EXPORT StartupData {
@@ -5464,6 +5466,7 @@ namespace internal {
 
 const int kApiPointerSize = sizeof(void*);  // NOLINT
 const int kApiIntSize = sizeof(int);  // NOLINT
+const int kApiInt64Size = sizeof(int64_t);  // NOLINT
 
 // Tag information for HeapObject.
 const int kHeapObjectTag = 1;
@@ -5562,13 +5565,23 @@ class Internals {
   static const int kExternalAsciiRepresentationTag = 0x06;
 
   static const int kIsolateEmbedderDataOffset = 0 * kApiPointerSize;
-  static const int kIsolateRootsOffset = 5 * kApiPointerSize;
+  static const int kAmountOfExternalAllocatedMemoryOffset =
+      4 * kApiPointerSize;
+  static const int kAmountOfExternalAllocatedMemoryAtLastGlobalGCOffset =
+      kAmountOfExternalAllocatedMemoryOffset + kApiInt64Size;
+  static const int kIsolateRootsOffset =
+      kAmountOfExternalAllocatedMemoryAtLastGlobalGCOffset + kApiInt64Size +
+      kApiPointerSize;
   static const int kUndefinedValueRootIndex = 5;
   static const int kNullValueRootIndex = 7;
   static const int kTrueValueRootIndex = 8;
   static const int kFalseValueRootIndex = 9;
   static const int kEmptyStringRootIndex = 162;
 
+  // The external allocation limit should be below 256 MB on all architectures
+  // to avoid that resource-constrained embedders run low on memory.
+  static const int kExternalAllocationLimit = 192 * 1024 * 1024;
+
   static const int kNodeClassIdOffset = 1 * kApiPointerSize;
   static const int kNodeFlagsOffset = 1 * kApiPointerSize + 3;
   static const int kNodeStateMask = 0xf;
@@ -6588,6 +6601,28 @@ uint32_t Isolate::GetNumberOfDataSlots() {
 }
 
 
+int64_t Isolate::AdjustAmountOfExternalAllocatedMemory(
+    int64_t change_in_bytes) {
+  typedef internal::Internals I;
+  int64_t* amount_of_external_allocated_memory =
+      reinterpret_cast<int64_t*>(reinterpret_cast<uint8_t*>(this) +
+                                 I::kAmountOfExternalAllocatedMemoryOffset);
+  int64_t* amount_of_external_allocated_memory_at_last_global_gc =
+      reinterpret_cast<int64_t*>(
+          reinterpret_cast<uint8_t*>(this) +
+          I::kAmountOfExternalAllocatedMemoryAtLastGlobalGCOffset);
+  int64_t amount = *amount_of_external_allocated_memory + change_in_bytes;
+  if (change_in_bytes > 0 &&
+      amount - *amount_of_external_allocated_memory_at_last_global_gc >
+          I::kExternalAllocationLimit) {
+    CollectAllGarbage("external memory allocation limit reached.");
+  } else {
+    *amount_of_external_allocated_memory = amount;
+  }
+  return *amount_of_external_allocated_memory;
+}
+
+
 template<typename T>
 void Isolate::SetObjectGroupId(const Persistent<T>& object,
                                UniqueId id) {