Explicitly keep default constructor in rules without members

R8 implicitly keeps the default constructor when no member rules are specified. Future versions of R8 will require apps to explicitly keep the default constructors that are required for the build to work.

This conservatively changes all keep rules that currently keep the default constructor to explicitly keep the default constructor.

Future work will attempt to tighten up the rules that do not require the default constructor to be kept.

Bug: 373579455
Test: existing
Change-Id: Idbadcd81d516f851cc9bfa1333d76f1036803291

Author: christofferqa

java/proguard.flags

@@ -1,11 +1,17 @@
 # Keep classes and methods that have the @UsedForTesting annotation
--keep @com.android.inputmethod.annotations.UsedForTesting class *
+# TODO(b/373579455): Evaluate if <init> needs to be kept.
+-keep @com.android.inputmethod.annotations.UsedForTesting class * {
+    void <init>();
+}
 -keepclassmembers class * {
     @com.android.inputmethod.annotations.UsedForTesting *;
 }
 
 # Keep classes and methods that have the @ExternallyReferenced annotation
--keep @com.android.inputmethod.annotations.ExternallyReferenced class *
+# TODO(b/373579455): Evaluate if <init> needs to be kept.
+-keep @com.android.inputmethod.annotations.ExternallyReferenced class * {
+    void <init>();
+}
 -keepclassmembers class * {
     @com.android.inputmethod.annotations.ExternallyReferenced *;
 }
@@ -17,11 +23,26 @@
 
 # Keep classes that are used as a parameter type of methods that are also marked as keep
 # to preserve changing those methods' signature.
--keep class com.android.inputmethod.latin.AssetFileAddress
--keep class com.android.inputmethod.latin.Dictionary
--keep class com.android.inputmethod.latin.NgramContext
--keep class com.android.inputmethod.latin.makedict.ProbabilityInfo
--keep class com.android.inputmethod.latin.utils.LanguageModelParam
+# TODO(b/373579455): Evaluate if <init> needs to be kept.
+-keep class com.android.inputmethod.latin.AssetFileAddress {
+    void <init>();
+}
+# TODO(b/373579455): Evaluate if <init> needs to be kept.
+-keep class com.android.inputmethod.latin.Dictionary {
+    void <init>();
+}
+# TODO(b/373579455): Evaluate if <init> needs to be kept.
+-keep class com.android.inputmethod.latin.NgramContext {
+    void <init>();
+}
+# TODO(b/373579455): Evaluate if <init> needs to be kept.
+-keep class com.android.inputmethod.latin.makedict.ProbabilityInfo {
+    void <init>();
+}
+# TODO(b/373579455): Evaluate if <init> needs to be kept.
+-keep class com.android.inputmethod.latin.utils.LanguageModelParam {
+    void <init>();
+}
 
 # TODO: remove once used in code.
 -keep class com.android.inputmethod.keyboard.KeyboardLayout { *; }