Make gvr_shim a component.

This is really what we ought to be doing to avoid ODR violations
caused by linking the prebuilt .a into multiple components, but
I previously couldn't see a way to link the .a into the component
.so with --whole-archive. However, it turns out that it's possible
using ldflags. This is a little hackish but it's probably better than
dealing with ODR violations.

Bug: 749784
Change-Id: I1ae275d57f36bc4a2c816d7f0ee8fdc4c000cf63
Reviewed-on: https://chromium-review.googlesource.com/1016092Reviewed-by: agrieve <agrieve@chromium.org>
Reviewed-by: Biao She <bshe@chromium.org>
Commit-Queue: Peter Collingbourne <pcc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551711}

third_party/gvr-android-sdk/BUILD.gn

@@ -98,13 +98,27 @@ config("libgvr_config") {
   include_dirs = [ "src/libraries/headers/" ]
 }
 
-source_set("gvr_shim") {
+component("gvr_shim") {
+  libs = [
+    "android",
+    "log",
+  ]
   if (enable_chrome_android_internal && !is_official_build) {
     deps = [
       "//clank/third_party/gvr_shim",
     ]
   } else {
-    libs =
+    libs +=
         [ "//third_party/gvr-android-sdk/libgvr_shim_static_${current_cpu}.a" ]
+
+    if (is_component_build) {
+      ldflags = [
+        "-Wl,--whole-archive",
+        rebase_path(
+            "//third_party/gvr-android-sdk/libgvr_shim_static_${current_cpu}.a",
+            root_build_dir),
+        "-Wl,--no-whole-archive",
+      ]
+    }
   }
 }