Providing min-sdk to Proguard

We had upstreamed min-sdk so that R8 could use it, but Proguard was forgotten.
This adds min-sdk support for Proguard.

Bug: 950918
Change-Id: I46aeb63ed89abcb2e384f874d3dbc1d43093884d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1559579
Commit-Queue: Sam Maier <smaier@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Sam Maier <smaier@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649230}

build/android/gyp/proguard.py

@@ -82,8 +82,6 @@ def _ParseOptions(args):
 
   assert not options.main_dex_rules_path or options.r8_path, \
       'R8 must be enabled to pass main dex rules.'
-  assert not options.min_api or options.r8_path, \
-      'R8 must be enabled to pass min api.'
 
   classpath = []
   for arg in options.classpath:
@@ -261,6 +259,7 @@ def main(args):
     proguard.mapping_output(options.mapping_output)
     proguard.libraryjars(libraries)
     proguard.verbose(options.verbose)
+    proguard.min_api(options.min_api)
     # Do not consider the temp file as an input since its name is random.
     input_paths = proguard.GetInputs()
 

build/android/gyp/util/proguard_util.py

@@ -53,6 +53,7 @@ class ProguardCmdBuilder(object):
     self._outjar = None
     self._mapping_output = None
     self._verbose = False
+    self._min_api = None
     self._disabled_optimizations = []
 
   def outjar(self, path):
@@ -93,6 +94,10 @@ class ProguardCmdBuilder(object):
   def verbose(self, verbose):
     self._verbose = verbose
 
+  def min_api(self, min_api):
+    assert self._min_api is None
+    self._min_api = min_api
+
   def disable_optimizations(self, optimizations):
     self._disabled_optimizations += optimizations
 
@@ -111,6 +116,13 @@ class ProguardCmdBuilder(object):
     if self._libraries:
       cmd += ['-libraryjars', ':'.join(self._libraries)]
 
+    if self._min_api:
+      cmd += [
+          '-assumevalues class android.os.Build$VERSION {' +
+          ' public static final int SDK_INT return ' + self._min_api +
+          '..9999; }'
+      ]
+
     for optimization in self._disabled_optimizations:
       cmd += [ '-optimizations', '!' + optimization ]
 

build/config/android/internal_rules.gni

@@ -1224,7 +1224,7 @@ if (enable_java_templates) {
           ]
         }
 
-        if (_proguarding_with_r8 && defined(invoker.min_sdk_version)) {
+        if (defined(invoker.min_sdk_version)) {
           args += [
             "--min-api",
             "${invoker.min_sdk_version}",