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..1445e4af2ab4c09c512919242c1793dbf9562fd1 100644
--- a/build/config/BUILDCONFIG.gn
+++ b/build/config/BUILDCONFIG.gn
@@ -111,11 +111,20 @@ if (current_os == "") {
 #   even if the value is overridden, which is wasteful. See first bullet.
 
 declare_args() {
-  # Component build.
+  # Component build. Setting to true compiles targets declared as "components"
+  # as shared libraries loaded dynamically. This speeds up development time.
+  # When false, components will be linked statically.
   is_component_build = false
 
-  # Debug build.
-  is_debug = true
+  # Set to enable the official build level of optimization. This has nothing
+  # to do with branding, but enables an additional level of optimization above
+  # release (!is_debug). This might be better expressed as a tri-state
+  # (debug, release, official) but for historical reasons there are two
+  # separate flags.
+  is_official_build = false
+
+  # Debug build. Enabling official builds automatically sets is_debug to false.
+  is_debug = !is_official_build
 
   # Whether we're a traditional desktop unix.
   is_desktop_linux = current_os == "linux"
@@ -136,6 +145,8 @@ declare_args() {
   # DON'T ADD MORE FLAGS HERE. Read the comment above.
 }
 
+assert(!(is_debug && is_official_build), "Can't do official debug builds")
+
 # ==============================================================================
 # TOOLCHAIN SETUP
 # ==============================================================================
@@ -596,23 +607,38 @@ 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 ||
+             (is_win && is_official_build)) {
+    # When there are no sources defined, use a source set to avoid creating
+    # an empty static library (which generally don't work).
+    #
+    # On Windows official builds, the link time code generation bloats static
+    # libraries to the point where some of them become >32 bits large which
+    # causes lib.exe to fail. Always use source sets for that configuration.
+    #
+    # TODO(brettw) bug 618797: Remove the mac condition. 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.