启动页Manifest中配置的theme，无法适配

### Environment
- [x] Autosize Version: 1.2.1
- [x] Target Android Version: 23
- [x] Device Model: All
- [x] Device Resolution: All
- [x] Design Size On AndroidManifest: 基于宽度 375dp

### 问题描述
启动页在AndroidManifest中设置了自定义的theme，大致就是logo+slogan这样的背景，用来优化启动的用户体验的，现在发现背景中的图片都不会自动适配。

### 原因分析
startActivity时在Activity的第一帧渲染之前，系统会自动添加一个startingWindow，这个window创建时会应用配置的theme，但是应用启动时使用的相关context关联的DisplayMetric没有进行适配，导致这个现象。

### 解决方案
目前没有想到很好的解决方案 - -！特来求助

### Related Code:
```java
// PhoneWindowManager.java
public StartingSurface addSplashScreen(IBinder appToken, String packageName, int theme,
CompatibilityInfo compatInfo, CharSequence nonLocalizedLabel, int labelRes, int icon,
int logo, int windowFlags, Configuration overrideConfig, int displayId) {

// 省略。。。
Context context = mContext;
if (DEBUG_SPLASH_SCREEN) Slog.d(TAG, "addSplashScreen " + packageName
+ ": nonLocalizedLabel=" + nonLocalizedLabel + " theme="
+ Integer.toHexString(theme));

// Obtain proper context to launch on the right display.
final Context displayContext = getDisplayContext(context, displayId);
if (displayContext == null) {
// Can't show splash screen on requested display, so skip showing at all.
return null;
}
context = displayContext;

if (theme != context.getThemeResId() || labelRes != 0) {
try {
context = context.createPackageContext(packageName, CONTEXT_RESTRICTED);
context.setTheme(theme);
} catch (PackageManager.NameNotFoundException e) {
// Ignore
}
}

if (overrideConfig != null && !overrideConfig.equals(EMPTY)) {
if (DEBUG_SPLASH_SCREEN) Slog.d(TAG, "addSplashScreen: creating context based"
+ " on overrideConfig" + overrideConfig + " for splash screen");
final Context overrideContext = context.createConfigurationContext(overrideConfig);
overrideContext.setTheme(theme);
final TypedArray typedArray = overrideContext.obtainStyledAttributes(
com.android.internal.R.styleable.Window);
final int resId = typedArray.getResourceId(R.styleable.Window_windowBackground, 0);
if (resId != 0 && overrideContext.getDrawable(resId) != null) {
// We want to use the windowBackground for the override context if it is
// available, otherwise we use the default one to make sure a themed starting
// window is displayed for the app.
if (DEBUG_SPLASH_SCREEN) Slog.d(TAG, "addSplashScreen: apply overrideConfig"
+ overrideConfig + " to starting window resId=" + resId);
context = overrideContext;
}
typedArray.recycle();
}

final PhoneWindow win = new PhoneWindow(context);
win.setIsStartingWindow(true);

CharSequence label = context.getResources().getText(labelRes, null);
// Only change the accessibility title if the label is localized
if (label != null) {
win.setTitle(label, true);
} else {
win.setTitle(nonLocalizedLabel, false);
}

win.setType(
WindowManager.LayoutParams.TYPE_APPLICATION_STARTING);

synchronized (mWindowManagerFuncs.getWindowManagerLock()) {
// Assumes it's safe to show starting windows of launched apps while
// the keyguard is being hidden. This is okay because starting windows never show
// secret information.
if (mKeyguardOccluded) {
windowFlags |= FLAG_SHOW_WHEN_LOCKED;
}
}

// Force the window flags: this is a fake window, so it is not really
// touchable or focusable by the user. We also add in the ALT_FOCUSABLE_IM
// flag because we do know that the next window will take input
// focus, so we want to get the IME window up on top of us right away.
win.setFlags(
windowFlags|
WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE|
WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE|
WindowManager.LayoutParams.FLAG_ALT_FOCUSABLE_IM,
windowFlags|
WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE|
WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE|
WindowManager.LayoutParams.FLAG_ALT_FOCUSABLE_IM);

win.setDefaultIcon(icon);
win.setDefaultLogo(logo);

win.setLayout(WindowManager.LayoutParams.MATCH_PARENT,
WindowManager.LayoutParams.MATCH_PARENT);

final WindowManager.LayoutParams params = win.getAttributes();
params.token = appToken;
params.packageName = packageName;
params.windowAnimations = win.getWindowStyle().getResourceId(
com.android.internal.R.styleable.Window_windowAnimationStyle, 0);
params.privateFlags |=
WindowManager.LayoutParams.PRIVATE_FLAG_FAKE_HARDWARE_ACCELERATED;
params.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_SHOW_FOR_ALL_USERS;

if (!compatInfo.supportsScreen()) {
params.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;
}

params.setTitle("Splash Screen " + packageName);
addSplashscreenContent(win, context);

wm = (WindowManager) context.getSystemService(WINDOW_SERVICE);
view = win.getDecorView();

if (DEBUG_SPLASH_SCREEN) Slog.d(TAG, "Adding splash screen window for "
+ packageName + " / " + appToken + ": " + (view.getParent() != null ? view : null));

wm.addView(view, params);
// 省略。。。

}

//AndroidManifest

// MainTheme

```

### Others: