[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 2016a6172093aadf755fe3240b3aedfed721cf9d..8ee19e3e97229ab2a1b515000f86a5566d74b05d 100644
--- a/content/app/content_main_runner.cc
+++ b/content/app/content_main_runner.cc
@@ -54,17 +54,13 @@
 #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"
 #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>
@@ -187,34 +183,50 @@ 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)
+  base::ScopedFD v8_context_fd =
+      file_descriptor_store.MaybeTakeFD(kV8ContextDataDescriptor, &region);

[Yuki, 2017/04/28 13:48:27]

Here and there, you seem calling "a snapshot of V8 context for the use in Blink"
"V8 context".  It seems quite confusing.

I'd propose the followings.
1) explicitly distinguish a snapshot of V8 context from a V8 context.
2) explicitly distinguish a snapshot of V8 context for Blink from the V8
snapshot of V8 built-in's.

For example, v8_context_snapshot_fd and kV8ContextSnapshotDataDescriptor, or,
considering that the owner is Blink (not V8), blink_v8_context_snapshot_fd
(Blink's snapshot of V8 context) and kBlinkV8ContextSnapshotDataDescriptor.

(I'd prefer the latter, but I think that not few people prefer the former.)

[peria, 2017/06/01 08:33:30]

Done.

+  if (v8_context_fd.is_valid()) {
+    gin::V8Initializer::LoadV8ContextFromFD(v8_context_fd.get(), region.offset,

[Yuki, 2017/04/28 13:48:27]

LoadV8ContextSnapshotFromFD?

[peria, 2017/06/01 08:33:31]

Done.

+                                            region.size);
+  } else {
+    gin::V8Initializer::LoadV8Context();
+  }
+#elif !defined(CHROME_MULTIPLE_DLL_BROWSER)
+  gin::V8Initializer::LoadV8Context();
+#endif  // OS
 }
 
 }  // namespace