Revert "[fuchsia] point to new location of mini_chromium"

This reverts commit 3676b71.

Reason for revert: By request of fangism: “We have an atomic change
problem and will need to re-roll this forward at a later date.”

Original change's description:
> [fuchsia] point to new location of mini_chromium
>
> Change-Id: I8aca564eeb3b579484048757e5da45bf0d25fc21
> Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/3089504
> Reviewed-by: Mark Mentovai <[email protected]>
> Commit-Queue: Mark Mentovai <[email protected]>

Change-Id: I1da123cd479e59029e267933ecc11451ddac3639
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/3104906
Reviewed-by: Mark Mentovai <[email protected]>
Commit-Queue: Mark Mentovai <[email protected]>

build/crashpad_buildconfig.gni

@@ -40,7 +40,7 @@ if (crashpad_is_external || crashpad_is_in_dart) {
   # External and Dart SDK builds assume crashpad and mini_chromium are peers.
   mini_chromium_source_parent = "../mini_chromium"
 } else if (crashpad_is_in_fuchsia) {
-  mini_chromium_source_parent = "//third_party/crashpad/third_party/mini_chromium"
+  mini_chromium_source_parent = "../third_party/mini_chromium"
 } else {
   mini_chromium_source_parent = "../third_party/mini_chromium"
 }
@@ -52,7 +52,7 @@ _mini_chromium_source_root = "$mini_chromium_source_parent/mini_chromium"
 if (crashpad_is_external || crashpad_is_in_dart) {
   mini_chromium_import_root = "../../$_mini_chromium_source_root"
 } else if (crashpad_is_in_fuchsia) {
-  mini_chromium_import_root = "//third_party/mini_chromium"
+  mini_chromium_import_root = _mini_chromium_source_root
 } else {
   mini_chromium_import_root = _mini_chromium_source_root
 }

third_party/mini_chromium/BUILD.gn

@@ -20,7 +20,7 @@ group("base") {
   } else if (crashpad_is_standalone) {
     public_deps = [ "mini_chromium/base" ]
   } else if (crashpad_is_in_fuchsia) {
-    public_deps = [ "//third_party/mini_chromium/base" ]
+    public_deps = [ "mini_chromium/base" ]
   } else if (crashpad_is_external) {
     public_deps = [ "../../../../mini_chromium/mini_chromium/base" ]
   } else if (crashpad_is_in_dart) {
@@ -39,10 +39,8 @@ group("base_test_support") {
 group("build") {
   if (crashpad_is_in_chromium) {
     # Chromium has no build target.
-  } else if (crashpad_is_standalone) {
+  } else if (crashpad_is_standalone || crashpad_is_in_fuchsia) {
     public_deps = [ "mini_chromium/build" ]
-  } else if (crashpad_is_in_fuchsia) {
-    public_deps = [ "//third_party/mini_chromium/build" ]
   } else if (crashpad_is_external) {
     public_deps = [ "../../../../mini_chromium/mini_chromium/build" ]
   } else if (crashpad_is_in_dart) {
@@ -53,10 +51,8 @@ group("build") {
 group("chromeos_buildflags") {
   if (crashpad_is_in_chromium) {
     public_deps = [ "//build:chromeos_buildflags" ]
-  } else if (crashpad_is_standalone) {
+  } else if (crashpad_is_standalone || crashpad_is_in_fuchsia) {
     public_deps = [ "mini_chromium/build:chromeos_buildflags" ]
-  } else if (crashpad_is_in_fuchsia) {
-    public_deps = [ "//third_party/mini_chromium/build:chromeos_buildflags" ]
   } else if (crashpad_is_external) {
     public_deps = [ "../../../../mini_chromium/mini_chromium/build:chromeos_buildflags" ]
   } else if (crashpad_is_in_dart) {