bind-gen: Add missing dependencies to v8_context_snapshot

The build rule of V8 context snapshot is missing some deps,
and this patch supplements them.

Bug: 839389
Change-Id: I875a194718f32d291b582da5071ec28dd992f08c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2307849
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790740}

third_party/blink/renderer/bindings/BUILD.gn

@@ -251,3 +251,16 @@ action_with_pydeps("generate_high_entropy_list") {
 
   deps = [ ":web_idl_database" ]
 }
+
+# Exposes the libraries that affect the resulting blob image of the V8 context
+# snapshot.
+group("v8_context_snapshot_influential_libs") {
+  visibility = []
+  visibility = [ "//tools/v8_context_snapshot/*" ]
+
+  public_deps = [
+    "//third_party/blink/renderer/core",
+    "//third_party/blink/renderer/modules",
+    "//third_party/blink/renderer/platform",
+  ]
+}

tools/v8_context_snapshot/BUILD.gn

@@ -64,12 +64,21 @@ if (use_v8_context_snapshot) {
     deps = [ ":v8_context_snapshot_generator($v8_snapshot_toolchain)" ]
 
     if (is_component_build) {
-      # In component builds, this forces the generator to rerun whenever the v8
-      # shared library is rebuilt. Without it would only regenerate if the
-      # generator itself was rebuilt.
-      inputs = [ "$root_out_dir/${shlib_prefix}v8${shlib_extension}" ]
+      # In the component build mode, the snapshot should be updated when any of
+      # the generator executable or the shared libraries get updated.  Note that
+      # it's possible that some of the shared libraries are updated without
+      # having the executable updated.
+      inputs = [
+        "$root_out_dir/${shlib_prefix}blink_core${shlib_extension}",
+        "$root_out_dir/${shlib_prefix}blink_modules${shlib_extension}",
+        "$root_out_dir/${shlib_prefix}blink_platform${shlib_extension}",
+        "$root_out_dir/${shlib_prefix}v8${shlib_extension}",
+      ]
 
-      deps += [ "//v8" ]
+      deps += [
+        "//third_party/blink/renderer/bindings:v8_context_snapshot_influential_libs",
+        "//v8",
+      ]
     }
 
     outputs = [ output_file ]