Revert of Remove unneeded split_count assignments (patchset #4 id:60001 of...

Revert of Remove unneeded split_count assignments (patchset #4 id:60001 of https://codereview.chromium.org/2311493002/ )

Reason for revert:
Due to this landing after my revert of Brett's change, it broke the world, e.g. https://build.chromium.org/p/chromium/builders/Android/builds/61684 . Since I'm not sure if the patch is quite right, I'll revert this too.

Original issue's description:
> Remove unneeded split_count assignments
>
> Refactoring of WebKit gn files has made splitting libraries less
> necessary. This broke generating of build files. This change
> removes the unneeded assignments.
>
> The error, in the generate_build_files step, was:
>
> C:\b\c\b\win_chrome\src\buildtools\win\gn.exe gen //out/Release --check
>   -> returned 1
> ERROR at //third_party/WebKit/Source/core/BUILD.gn:52:19: Assignment had no effect.
>     split_count = 5
>                   ^
> You set the variable "split_count" here and it was unused before it went
> out of scope.
> See //third_party/WebKit/public/BUILD.gn:53:5: which caused the file to be included.
>     "//third_party/WebKit/Source/core",
>     ^---------------------------------
> GN gen failed: 1
>
> It first appeared in build 10455:
> https://build.chromium.org/p/chromium.chrome/builders/Google%20Chrome%20Win/builds/10455/steps/generate_build_files/logs/stdio
>
> Suspect is crrev.com/2299143005
>
> TBR=brettw@chromium.org
>
> Committed: https://crrev.com/f7d8febdf0166e2193b5e34e81b6b9dfb9ffd7c4
> Cr-Commit-Position: refs/heads/master@{#416441}

TBR=brettw@chromium.org,brucedawson@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2303293004
Cr-Commit-Position: refs/heads/master@{#416443}

third_party/WebKit/Source/core/BUILD.gn

@@ -45,6 +45,16 @@ config("core_include_dirs") {
   }
 }
 
+if (!is_component_build) {
+  if (is_win && is_official_build) {
+    # Shard this target into parts to work around linker limitations
+    # on link time code generation builds.
+    split_count = 5
+  } else {
+    split_count = 1
+  }
+}
+
 source_set("generated") {
   deps = [
     ":core_generated",
@@ -184,18 +194,11 @@ target(core_link_large_target_type, "svg") {
 }
 
 target(core_link_large_target_type, "remaining") {
-  if (core_link_large_target_type == "split_static_library") {
+  if (is_win && is_official_build &&
+      core_link_large_target_type == "split_static_library") {
     # Shard this target into parts to work around linker limitations
     # on link time code generation builds.
-    if (is_win) {
-      if (is_official_build) {
-        split_count = 19
-      } else {
-        split_count = 5
-      }
-    } else {
-      split_count = 1
-    }
+    split_count = 19
   }
 
   # This is currently a mashup of "webcore_rendering" and "webcore_remaining"