Make standalone webview crash dump percentage contingent on channel

We currently submit a manual CL every time we want to change the
hardcoded crash dump percentage for standalone webview due to releasing
a beta apk or promoting a beta to stable.

Now that standalone webview has channels
(https://bugs.chromium.org/p/chromium/issues/detail?id=919216), add
logic to include different crash reporting rates for different channels.

Bug: 954298
Change-Id: I3a6a9e32e67260cdb2190ea5b394c514d6df0c06
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1574362Reviewed-by: Tao Bai <michaelbai@chromium.org>
Commit-Queue: Drew Stonebraker <stonebraker@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652426}

android_webview/common/crash_reporter/aw_crash_reporter_client.cc

@@ -27,6 +27,8 @@
 
 namespace android_webview {
 
+constexpr unsigned int kCrashDumpPercentageForStable = 1;
+
 namespace {
 
 class AwCrashReporterClient : public crash_reporter::CrashReporterClient {
@@ -76,6 +78,9 @@ class AwCrashReporterClient : public crash_reporter::CrashReporterClient {
       return 100;
     }
 
+    if (version_info::android::GetChannel() == version_info::Channel::STABLE)
+      return kCrashDumpPercentageForStable;
+
     return 100;
   }