Auto merge of #15773 - MortimerGoro:android_improvements, r=larsbergstrom,fabricedesre

Android life cycle improvements and Gradle integration

This PR includes Android life cycle Improvements and Gradle integration for android packaging.

Android life cycle improvements are implemented in both the new [MainActivity](https://github.com/servo/servo/compare/master...MortimerGoro:android_improvements?expand=1#diff-f43708b102e98272c2af7454b8846927) and native code in this related PR: https://github.com/servo/glutin/pull/117
- Properly handle the life cycle of the Android Activity: manage EGLContext lost & restore, and animation loop pause/resume when the app goes to background/foreground or orientation changes. In the current upstream Servo crashes when the app goes to background, activity stops or changes orientation
- Handle event loop awake for Servo Animation loop
- Handle screen resize & orientation events
- Implement new keep_screen_on preference which keeps Android device's screen from ever going to sleep: very useful for games or WebVR
- Implement a full screen mode enabled by preference: very useful for games or WebVR
- Implement new shell.native-orientation preference which allows to lock the Activity to a specific orientation
- Automatically sync new android assets to sdcard when the Android version code is changed.  In the current upstream only the existence of the folder is check but resources are not updated

ofscreen_gl_context is updated to fix this: https://github.com/emilio/rust-offscreen-rendering-context/pull/83

This PR integrates Gradle build system for android packaging. Most of the code is implemented in this [build.gradle](https://github.com/servo/servo/compare/master...MortimerGoro:android_improvements?expand=1#diff-89cdb9324addb994cdba0a158b209547) . We can get rid of [build-apk](https://github.com/servo/servo/compare/master...MortimerGoro:android_improvements?expand=1#diff-40f5a7cf22f94aad059b2c1795347f5e) and manual jar dependency copying in the [package_commands.py](https://github.com/servo/servo/compare/master...MortimerGoro:android_improvements?expand=1#diff-0d425b142c8d10ae6ac1f3711fb5c23a). The correct version of gradle is automatically downloaded using the gradlew wrapper.

Some improvements:
- Allows to include more complex android dependencies/SDKs like AARs, manifest auto-merging and more.
- Improved packaging process: The gradle project is always in the same folder, it uses relative paths for everything (assets, native libraries) and outputs the apk into the correct target folder in servo. In the current upstream, ant/python build system copies the manifest, project, resources and jars each time so you end with multiple copies of the same files.
- Improved dependency declaration. We do not have to manually copy jar dependencies in the python script anymore. The gradle build scripts itself is able to search for the dependencies in the correct servo target folder.
- Supports packaging apks with different architectures: armeabi, armeabi-v7a, aarch64. We still need to fix some native servo compilation issues with armeabi-v7a, aarch64 due to dependencies which use `make`. I'll push this changes in a separate PR of the python build files but the gradle file is already ready to handle that.
- We can easily create product flavors for different versions of Servo. For example a default browser, a WebVR browser with additional dependencies or a Servo android Webview component
- Fixes minor.major.52 build error when blurdroid cargo dependency is compiled using java8 (the default in new Linux machines). The gradle build file enables the new Jack compiler which supports Java8 dependencies.
- The project can be opened with Android Studio and run the brand new GPU debugger on any Android phone. I'll add some docs in the Wiki about this.

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #14568 (github issue number if applicable).

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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components/config/Cargo.toml

@@ -27,3 +27,6 @@ env_logger = "0.4"
 
 [target.'cfg(all(unix, not(target_os = "macos"), not(target_os = "ios"), not(target_os = "android")))'.dependencies]
 xdg = "2.0"
+
+[target.'cfg(target_os = "android")'.dependencies]
+android_injected_glue = {git = "https://github.com/mmatyas/android-rs-injected-glue"}

components/config/basedir.rs

@@ -6,8 +6,12 @@
 //! For linux based platforms, it uses the XDG base directory spec but provides
 //! similar abstractions for non-linux platforms.
 
+#[cfg(target_os = "android")]
+use android_injected_glue;
 #[cfg(any(target_os = "macos", target_os = "windows"))]
 use std::env;
+#[cfg(target_os = "android")]
+use std::ffi::CStr;
 use std::path::PathBuf;
 #[cfg(all(unix, not(target_os = "macos"), not(target_os = "ios"), not(target_os = "android")))]
 use xdg;
@@ -20,8 +24,12 @@ pub fn default_config_dir() -> Option<PathBuf> {
 }
 
 #[cfg(target_os = "android")]
+#[allow(unsafe_code)]
 pub fn default_config_dir() -> Option<PathBuf> {
-    Some(PathBuf::from("/sdcard/servo"))
+    let dir = unsafe {
+        CStr::from_ptr((*android_injected_glue::get_app().activity).externalDataPath)
+    };
+    Some(PathBuf::from(dir.to_str().unwrap()))
 }
 
 #[cfg(all(unix, not(target_os = "macos"), not(target_os = "ios"), not(target_os = "android")))]
@@ -32,8 +40,12 @@ pub fn default_data_dir() -> Option<PathBuf> {
 }
 
 #[cfg(target_os = "android")]
+#[allow(unsafe_code)]
 pub fn default_data_dir() -> Option<PathBuf> {
-    Some(PathBuf::from("/sdcard/servo"))
+    let dir = unsafe {
+        CStr::from_ptr((*android_injected_glue::get_app().activity).internalDataPath)
+    };
+    Some(PathBuf::from(dir.to_str().unwrap()))
 }
 
 #[cfg(all(unix, not(target_os = "macos"), not(target_os = "ios"), not(target_os = "android")))]
@@ -44,8 +56,14 @@ pub fn default_cache_dir() -> Option<PathBuf> {
 }
 
 #[cfg(target_os = "android")]
+#[allow(unsafe_code)]
 pub fn default_cache_dir() -> Option<PathBuf> {
-    Some(PathBuf::from("/sdcard/servo"))
+    // TODO: Use JNI to call context.getCacheDir().
+    // There is no equivalent function in NDK/NativeActivity.
+    let dir = unsafe {
+        CStr::from_ptr((*android_injected_glue::get_app().activity).externalDataPath)
+    };
+    Some(PathBuf::from(dir.to_str().unwrap()))
 }
 
 #[cfg(target_os = "macos")]

components/config/lib.rs

@@ -4,6 +4,8 @@
 
 #![deny(unsafe_code)]
 
+#[cfg(target_os = "android")]
+extern crate android_injected_glue;
 extern crate euclid;
 extern crate getopts;
 #[macro_use] extern crate lazy_static;

components/config/resource_files.rs

@@ -2,8 +2,12 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+#[cfg(target_os = "android")]
+use android_injected_glue;
 #[cfg(not(target_os = "android"))]
 use std::env;
+#[cfg(target_os = "android")]
+use std::ffi::CStr;
 use std::fs::File;
 use std::io::{self, Read};
 use std::path::{Path, PathBuf};
@@ -21,8 +25,12 @@ pub fn set_resources_path(path: Option<String>) {
 }
 
 #[cfg(target_os = "android")]
+#[allow(unsafe_code)]
 pub fn resources_dir_path() -> io::Result<PathBuf> {
-    Ok(PathBuf::from("/sdcard/servo/"))
+    let dir = unsafe {
+        CStr::from_ptr((*android_injected_glue::get_app().activity).externalDataPath)
+    };
+    Ok(PathBuf::from(dir.to_str().unwrap()))
 }
 
 #[cfg(not(target_os = "android"))]