android_webview: Allow V8 to be built even when chromium is prebuilt.

Android.mk

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This Android makefile is used to build WebView in the Android build system.
 # gyp autogenerates most of the real makefiles, which we include below.
 
-# Don't do anything if the product is using a prebuilt webviewchromium, to avoid
-# duplicate target definitions between this directory and the prebuilts.
-ifneq ($(PRODUCT_PREBUILT_WEBVIEWCHROMIUM),yes)
-
-CHROMIUM_DIR := $(call my-dir)
+LOCAL_PATH := $(call my-dir)
+CHROMIUM_DIR := $(LOCAL_PATH)
 
 # We default to release for the Android build system. Developers working on
 # WebView code can build with "make GYP_CONFIGURATION=Debug".
 GYP_CONFIGURATION := Release
 
-# Include the manually-written makefile that builds all the WebView java code.
+# If the product is using a prebuilt libwebviewchromium then we need to skip
+# including most of the makefiles to avoid duplicate target definitions. Some
+# targets are still needed, so list their makefiles explicitly.
+ifeq ($(PRODUCT_PREBUILT_WEBVIEWCHROMIUM),yes)
+GYP_MAKEFILE_STEMS := \
+        $(addprefix $(CHROMIUM_DIR)/v8/tools/gyp/, \
+                generate_trig_table.host \
+                js2c.host \
+                mksnapshot.host \
+                v8_base.host \
+                v8_libbase.host \
+                v8_nosnapshot.host \
+                v8_base.target \
+                v8_libbase.target \
+                v8_snapshot.target \
+        ) \
+        $(addprefix $(CHROMIUM_DIR)/third_party/icu/, \
+                icudata.host \
+                icui18n.host \
+                icuuc.host \
+                icui18n.target \
+                icuuc.target \
+                system_icu.target \
+        )
+else
+# Not using a prebuilt; include the manually-written makefile that builds all
+# the WebView java code, and use the main autogenerated makefile.
 include $(CHROMIUM_DIR)/android_webview/Android.mk
+GYP_MAKEFILE_STEMS := $(CHROMIUM_DIR)/GypAndroid
+endif
 
 # If the gyp-generated makefile exists for the current host OS and primary
 # target architecture, we need to include it. If it doesn't exist then just do
 # nothing, since we may not have finished bringing up this architecture yet.
 ifneq (,$(wildcard $(CHROMIUM_DIR)/GypAndroid.$(HOST_OS)-$(TARGET_ARCH).mk))
 
 # We set GYP_VAR_PREFIX to the empty string to indicate that we are building for
 # the primary target architecture.
 GYP_VAR_PREFIX :=
 
 # If the host is declared as being 64-bit, set the host multilib variables
 # appropriately to ensure that the host targets are the same "bitness" as the
 # primary target, which is required by V8.
 ifeq ($(HOST_IS_64_BIT),true)
 ifeq ($(TARGET_IS_64_BIT),true)
 GYP_HOST_VAR_PREFIX :=
 GYP_HOST_MULTILIB := 64
 else  # Target is 32-bit.
 GYP_HOST_VAR_PREFIX := $(HOST_2ND_ARCH_VAR_PREFIX)
 GYP_HOST_MULTILIB := 32
 endif
 endif
 
-include $(CHROMIUM_DIR)/GypAndroid.$(HOST_OS)-$(TARGET_ARCH).mk
+# Include the appropriate version of each of the makefiles.
+include $(addsuffix .$(HOST_OS)-$(TARGET_ARCH).mk,$(GYP_MAKEFILE_STEMS))
 
 endif  # End primary architecture handling.
 
 # Do the same check for the secondary architecture; if this doesn't exist then
 # the current target platform probably doesn't have a secondary architecture and
 # we can just do nothing.
 ifneq (,$(wildcard $(CHROMIUM_DIR)/GypAndroid.$(HOST_OS)-$(TARGET_2ND_ARCH).mk))
 
 # We set GYP_VAR_PREFIX to $(TARGET_2ND_ARCH_VAR_PREFIX) to indicate that we are
 # building for the secondary target architecture.
 GYP_VAR_PREFIX := $(TARGET_2ND_ARCH_VAR_PREFIX)
 
 # If the host is declared as being 64-bit, set the host multilib variables
 # appropriately to ensure that the host targets are the same "bitness" as the
 # secondary target, which is required by V8.
 ifeq ($(HOST_IS_64_BIT),true)
 ifeq ($(2ND_TARGET_IS_64_BIT),true)
 GYP_HOST_VAR_PREFIX :=
 GYP_HOST_MULTILIB := 64
 else  # Second target is 32-bit.
 GYP_HOST_VAR_PREFIX := $(HOST_2ND_ARCH_VAR_PREFIX)
 GYP_HOST_MULTILIB := 32
 endif
 endif
 
-include $(CHROMIUM_DIR)/GypAndroid.$(HOST_OS)-$(TARGET_2ND_ARCH).mk
+# Include the appropriate version of each of the makefiles.
+include $(addsuffix .$(HOST_OS)-$(TARGET_2ND_ARCH).mk,$(GYP_MAKEFILE_STEMS))
 
 endif  # End secondary architecture handling.
-
-endif