[Bindings] Create and use V8 context snapshots

content/app/content_main_runner.cc

Index: content/app/content_main_runner.cc
diff --git a/content/app/content_main_runner.cc b/content/app/content_main_runner.cc
index a677c9d2c6df30e78614b09d396372db33dff781..77efd83eaecbd68adc6a22cf9f31c6fc5aa709e9 100644
--- a/content/app/content_main_runner.cc
+++ b/content/app/content_main_runner.cc
@@ -54,6 +54,7 @@
 #include "content/public/common/content_switches.h"
 #include "content/public/common/main_function_params.h"
 #include "content/public/common/sandbox_init.h"
+#include "gin/v8_initializer.h"
 #include "ipc/ipc_descriptors.h"
 #include "media/base/media.h"
 #include "ppapi/features/features.h"
@@ -61,11 +62,6 @@
 #include "ui/base/ui_base_paths.h"
 #include "ui/base/ui_base_switches.h"
 
-#if defined(V8_USE_EXTERNAL_STARTUP_DATA) && \
-    !defined(CHROME_MULTIPLE_DLL_BROWSER)
-#include "gin/v8_initializer.h"
-#endif
-
 #if defined(OS_WIN)
 #include <malloc.h>
 #include <cstring>
@@ -188,34 +184,50 @@ void InitializeV8IfNeeded(
   if (process_type == switches::kGpuProcess)
     return;
 
-#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
   base::FileDescriptorStore& file_descriptor_store =
       base::FileDescriptorStore::GetInstance();
   base::MemoryMappedFile::Region region;
+#endif
+
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
   base::ScopedFD v8_snapshot_fd =
       file_descriptor_store.MaybeTakeFD(kV8SnapshotDataDescriptor, &region);
   if (v8_snapshot_fd.is_valid()) {
     gin::V8Initializer::LoadV8SnapshotFromFD(v8_snapshot_fd.get(),
                                              region.offset, region.size);
-    } else {
-      gin::V8Initializer::LoadV8Snapshot();
-    }
-    base::ScopedFD v8_natives_fd =
-        file_descriptor_store.MaybeTakeFD(kV8NativesDataDescriptor, &region);
-    if (v8_natives_fd.is_valid()) {
-      gin::V8Initializer::LoadV8NativesFromFD(v8_natives_fd.get(),
-                                              region.offset, region.size);
-    } else {
-      gin::V8Initializer::LoadV8Natives();
-    }
-#else
-#if !defined(CHROME_MULTIPLE_DLL_BROWSER)
+  } else {
     gin::V8Initializer::LoadV8Snapshot();
+  }
+  base::ScopedFD v8_natives_fd =
+      file_descriptor_store.MaybeTakeFD(kV8NativesDataDescriptor, &region);
+  if (v8_natives_fd.is_valid()) {
+    gin::V8Initializer::LoadV8NativesFromFD(v8_natives_fd.get(), region.offset,
+                                            region.size);
+  } else {
     gin::V8Initializer::LoadV8Natives();
+  }
+#else
+#if !defined(CHROME_MULTIPLE_DLL_BROWSER)
+  gin::V8Initializer::LoadV8Snapshot();
+  gin::V8Initializer::LoadV8Natives();
 #endif  // !CHROME_MULTIPLE_DLL_BROWSER
 #endif  // OS_POSIX && !OS_MACOSX
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
+
+#if defined(OS_POSIX) && !defined(OS_MACOSX)

[haraken, 2017/05/20 19:10:01]

Does this mean that we don't support the context snapshot on Win?

[peria, 2017/05/30 08:25:43]

unfortunately, I'm not sure.
This follows the routine of V8 native+snapshot.

+  base::ScopedFD v8_context_fd =
+      file_descriptor_store.MaybeTakeFD(kV8ContextDataDescriptor, &region);
+  if (v8_context_fd.is_valid()) {
+    gin::V8Initializer::LoadV8ContextFromFD(v8_context_fd.get(), region.offset,
+                                            region.size);
+  } else {

[haraken, 2017/05/20 19:10:01]

When do we hit this else branch?

[peria, 2017/05/30 08:25:43]

ditto.

+    gin::V8Initializer::LoadV8Context();
+  }
+#elif !defined(CHROME_MULTIPLE_DLL_BROWSER)
+  gin::V8Initializer::LoadV8Context();
+#endif  // OS
 }
 
 }  // namespace