Fallback to software TPM if needed

Use software TPM implementation by default if
tpm_fallback=true is in build arguments

TEST=manual
BUG=b:146479130

Change-Id: Ibc6e17c97554ee6c685cedff9ca0b11bea738f2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2062995
Commit-Queue: Taras Antoshchuk <tantoshchuk@google.com>
Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Polina Bondarenko <pbond@chromium.org>
Auto-Submit: Taras Antoshchuk <tantoshchuk@google.com>
Cr-Commit-Position: refs/heads/master@{#746308}

chrome/browser/BUILD.gn

@@ -5432,6 +5432,10 @@ jumbo_static_library("browser") {
   if (is_android && notouch_build) {
     configs += [ ":notouch_config" ]
   }
+
+  if (tpm_fallback) {
+    defines += [ "TPM_FALLBACK" ]
+  }
 }
 
 config("notouch_config") {

chrome/browser/buildflags.gni

@@ -4,4 +4,5 @@
 
 declare_args() {
   enable_kaleidoscope = false
+  tpm_fallback = false
 }

chrome/browser/profiles/profile_io_data.cc

@@ -181,6 +181,14 @@ void StartTPMSlotInitializationOnIOThread(const AccountId& account_id,
       base::BindOnce(&GetTPMInfoForUserOnUIThread, account_id, username_hash));
 }
 
+bool IsTPMTokenEnabledForNSS() {
+#if !defined(TPM_FALLBACK)
+  return crypto::IsTPMTokenEnabledForNSS();
+#else
+  return false;
+#endif
+}
+
 void StartNSSInitOnIOThread(const AccountId& account_id,
                             const std::string& username_hash,
                             const base::FilePath& path) {
@@ -199,7 +207,7 @@ void StartNSSInitOnIOThread(const AccountId& account_id,
 
   crypto::WillInitializeTPMForChromeOSUser(username_hash);
 
-  if (crypto::IsTPMTokenEnabledForNSS()) {
+  if (IsTPMTokenEnabledForNSS()) {
     if (crypto::IsTPMTokenReady(
             base::Bind(&StartTPMSlotInitializationOnIOThread, account_id,
                        username_hash))) {