Auto merge of #20912 - paulrouget:androidv2, r=jdm,mortimergoro,simonsapin

Revisit how the Android port works.

Fix #20855
Fix #18625
Fix #21147

Before polishing and making sure everything works fine (like the VR code, the android-x86 version, the non-android version of the lib, …), I'd like to get some early feedback on the approach.

I recommend reviewing commit by commit.

To test, just follow the regular steps:

```
    ./mach build -d --android
    ./mach package --dev --android builds servo.apk
    ./mach install --dev --android && ./mach run --android
```

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

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

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components/config/Cargo.toml

@@ -30,6 +30,3 @@ embedder_traits = { path = "../embedder_traits", features = ["tests"] }
 
 [target.'cfg(not(target_os = "android"))'.dependencies]
 dirs = "1.0"
-
-[target.'cfg(target_os = "android")'.dependencies]
-android_injected_glue = "0.2"

components/config/basedir.rs

@@ -6,41 +6,33 @@
 //! 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(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")))]
-pub fn default_config_dir() -> PathBuf {
+pub fn default_config_dir() -> Option<PathBuf> {
     let mut config_dir = ::dirs::config_dir().unwrap();
     config_dir.push("servo");
     config_dir.push("default");
-    config_dir
+    Some(config_dir)
 }
 
 #[cfg(target_os = "android")]
-#[allow(unsafe_code)]
-pub fn default_config_dir() -> PathBuf {
-    let dir = unsafe {
-        CStr::from_ptr((*android_injected_glue::get_app().activity).externalDataPath)
-    };
-    PathBuf::from(dir.to_str().unwrap())
+pub fn default_config_dir() -> Option<PathBuf> {
+    None
 }
 
 #[cfg(target_os = "macos")]
-pub fn default_config_dir() -> PathBuf {
+pub fn default_config_dir() -> Option<PathBuf> {
     // FIXME: use `config_dir()` ($HOME/Library/Preferences)
     // instead of `data_dir()` ($HOME/Library/Application Support) ?
     let mut config_dir = ::dirs::data_dir().unwrap();
     config_dir.push("Servo");
-    config_dir
+    Some(config_dir)
 }
 
 #[cfg(target_os = "windows")]
-pub fn default_config_dir() -> PathBuf {
+pub fn default_config_dir() -> Option<PathBuf> {
     let mut config_dir = ::dirs::config_dir().unwrap();
     config_dir.push("Servo");
-    config_dir
+    Some(config_dir)
 }

components/config/lib.rs

@@ -4,8 +4,6 @@
 
 #![deny(unsafe_code)]
 
-#[cfg(target_os = "android")]
-extern crate android_injected_glue;
 #[cfg(not(target_os = "android"))]
 extern crate dirs;
 extern crate embedder_traits;

components/config/prefs.rs

@@ -183,9 +183,10 @@ pub fn add_user_prefs() {
             init_user_prefs(&mut path);
         }
         None => {
-            let mut path = default_config_dir();
-            if path.join("prefs.json").exists() {
-                init_user_prefs(&mut path);
+            if let Some(mut path) = default_config_dir() {
+                if path.join("prefs.json").exists() {
+                    init_user_prefs(&mut path);
+                }
             }
         }
     }

components/config/tests/prefs.rs

@@ -48,6 +48,7 @@ fn test_get_set_reset_extend() {
     assert_eq!(*PREFS.get("extra.stuff"), PrefValue::Boolean(false));
 }
 
+#[cfg(not(target_os = "android"))]
 #[test]
 fn test_default_config_dir_create_read_write() {
   let json_str = "{\
@@ -56,7 +57,7 @@ fn test_default_config_dir_create_read_write() {
   \"shell.homepage\": \"https://google.com\"\
 }";
     let mut expected_json = String::new();
-    let config_path = basedir::default_config_dir();
+    let config_path = basedir::default_config_dir().unwrap();
 
     if !config_path.exists() {
       fs::create_dir_all(&config_path).unwrap();