Revert "Use .r8dex.jar and .mergeddex.jar rather than .dex.zip"

This reverts commit 89a7ef17.

Reason for revert: This is breaking WebView bundles on the official builders, see crbug.com/1069724. It looks like bundletool looks specifically for .dex extensions[1], and this change breaks that assumption.

1. https://github.com/google/bundletool/blob/3586f8630e08733503ddbd1e74e10d4fb50e0d69/src/main/java/com/android/tools/build/bundletool/validation/DexFilesValidator.java#L48

Original change's description:
> Use .r8dex.jar and .mergeddex.jar rather than .dex.zip
> 
> This just renames the extensions in order to make build speed summaries
> distinguish the two.
> 
> Bug: 1067273
> Change-Id: I0a1e14cfed3557d29cd6beb0987436cacfaf6b65
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2140908
> Commit-Queue: Andrew Grieve <agrieve@chromium.org>
> Commit-Queue: Peter Wen <wnwen@chromium.org>
> Auto-Submit: Andrew Grieve <agrieve@chromium.org>
> Reviewed-by: Peter Wen <wnwen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#757855}

TBR=wnwen@chromium.org,agrieve@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1067273, 1069724
Change-Id: Ied71fc35aef250bdbf21ee4ec34f5bb2d0eb3423
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2145860Reviewed-by: Clark DuVall <cduvall@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758275}

build/android/docs/java_toolchain.md

@@ -145,12 +145,12 @@ This step happens only when targets have `supports_android = true`.
 This step is skipped when building using [Incremental Install].
 
 When `is_java_debug = true`:
-* [d8] merges all library `.dex.jar` files into a final `.mergeddex.jar`.
+* [d8] merges all library `.dex.jar` files into a final `.dex.zip`.
 
 When `is_java_debug = false`:
 * [R8] performs whole-program optimization on all library `lib.java` `.jar`
-  files and outputs a final `.r8dex.jar`.
-  * For App Bundles, R8 creates a single `.r8dex.jar` with the code from all
+  files and outputs a final `.dex.zip`.
+  * For App Bundles, R8 creates a single `.dex.zip` with the code from all
     modules.
 
 [Incremental Install]: /build/android/incremental_install/README.md
@@ -160,7 +160,7 @@ When `is_java_debug = false`:
 
 This step happens only when `is_java_debug = false`.
 
-* [dexsplitter.py] splits the single `*dex.jar` into per-module `*dex.jar`
+* [dexsplitter.py] splits the single `.dex.zip` into per-module `.dex.zip`
   files.
 
 ## Test APKs with apk_under_test

build/android/gyp/dex.py

@@ -258,7 +258,7 @@ def _ZipMultidex(file_dir, dex_files):
   """
   ordered_files = []  # List of (archive name, file name)
   for f in dex_files:
-    if f.endswith('dex.jar'):
+    if f.endswith('classes.dex.zip'):
       ordered_files.append(('classes.dex', f))
       break
   if not ordered_files:

build/android/gyp/dexsplitter.py

@@ -101,15 +101,15 @@ def main(args):
         if os.path.exists(module_dex_file):
           curr_location_to_dest.append((module_dex_file, dest))
         else:
-          module_dex_file += '.jar'
+          module_dex_file += '.zip'
           assert os.path.exists(
               module_dex_file), 'Dexsplitter tool output not found.'
-          curr_location_to_dest.append((module_dex_file + '.jar', dest))
+          curr_location_to_dest.append((module_dex_file + '.zip', dest))
 
     for curr_location, dest in curr_location_to_dest:
       with build_utils.AtomicOutput(dest) as f:
-        if curr_location.endswith('.jar'):
-          if dest.endswith('.jar'):
+        if curr_location.endswith('.zip'):
+          if dest.endswith('.zip'):
             shutil.copy(curr_location, f.name)
           else:
             with zipfile.ZipFile(curr_location, 'r') as z:
@@ -119,7 +119,7 @@ def main(args):
                   options.input_dex_zip)
               z.extract(namelist[0], f.name)
         else:
-          if dest.endswith('.jar'):
+          if dest.endswith('.zip'):
             build_utils.ZipDir(
                 f.name, os.path.abspath(os.path.join(curr_location, os.pardir)))
           else:

build/config/android/rules.gni

@@ -2349,7 +2349,7 @@ if (enable_java_templates) {
         defined(invoker.static_library_dependent_targets) && _proguard_enabled
     if (_is_static_library_provider) {
       _static_library_sync_dex_path =
-          "$_out_dir/static_library_synchronized_proguard.r8dex.jar"
+          "$_out_dir/static_library_synchronized_proguard.classes.dex.zip"
       _resource_ids_provider_deps = []
       foreach(_target, invoker.static_library_dependent_targets) {
         if (_target.is_resource_ids_provider) {
@@ -2397,11 +2397,7 @@ if (enable_java_templates) {
     if (!_incremental_apk) {
       # Bundle modules don't build the dex here, but need to write this path
       # to their .build_config file.
-      if (_proguard_enabled) {
-        _final_dex_path = "$_base_path.r8dex.jar"
-      } else {
-        _final_dex_path = "$_base_path.mergeddex.jar"
-      }
+      _final_dex_path = "$_out_dir/classes.dex.zip"
     }
 
     _android_manifest =