Default components to static libraries in GN build

build/config/BUILDCONFIG.gn

Index: build/config/BUILDCONFIG.gn
diff --git a/build/config/BUILDCONFIG.gn b/build/config/BUILDCONFIG.gn
index a55a56582fb4912befa3719d03e1fc7a9fb1c489..c5632550252a8999f40091b1ccff2b75629b72c4 100644
--- a/build/config/BUILDCONFIG.gn
+++ b/build/config/BUILDCONFIG.gn
@@ -596,23 +596,32 @@ set_defaults("test") {
 # ==============================================================================
 
 # Defines a component, which equates to a shared_library when
-# is_component_build == true and a source_set / static_library otherwise.
+# is_component_build == true and a static_library otherwise.
 #
-# Arguments are the same as a normal library with this addition:
-#   component_never_use_source_set: Whether to use static_library instead of
-#       source_set for non-component builds. Some targets (e.g. //base) should
-#       use static_library rather than source_set to avoid linking unused object
-#       files.
+# Use static libraries for the static build rather than source sets because
+# many of of our test binaries link many large dependencies but often don't
+# use large portions of them. The static libraries are much more efficient to
+# link in this situation since only the necessary object files are linked.
+#
+# The invoker can override the type of the target in the non-component-build
+# case by setting static_component_type to either "source_set" or
+# "static_library". If unset, the default will be used.
 template("component") {
-  _never_use_source_set = defined(invoker.component_never_use_source_set) &&
-                          invoker.component_never_use_source_set
-  assert(_never_use_source_set || true)  # Mark as used.
   if (is_component_build) {
     _component_mode = "shared_library"
-  } else if (_never_use_source_set) {
-    _component_mode = "static_library"
-  } else {
+  } else if (defined(invoker.static_component_type)) {
+    assert(invoker.static_component_type == "static_library" ||
+           invoker.static_component_type == "source_set")
+    _component_mode = invoker.static_component_type
+  } else if (!defined(invoker.sources) || is_mac) {
+    # When there are no sources defined, use a source set to avoid creating
+    # an empty static library (which generally don't work).
+    #
+    # TODO(brettw) bug 618797: On Mac making these as static_library causes
+    # crashes. Remove the mac condition above when this is fixed.
     _component_mode = "source_set"
+  } else {
+    _component_mode = "static_library"
   }
   target(_component_mode, target_name) {
     # Explicitly forward visibility, implicitly forward everything else.