MAGETWO-63444: Remove object from cache in \Magento\Theme\Model\Theme\ThemeProvider

- ThemeProvider: Fix inheritdoc blocks. Replace docblock with inline comment.
- ThemeProviderTest: Self document assertions with message parameter instead of comments.

Author: tjwiebell

app/code/Magento/Theme/Model/Theme/ThemeProvider.php

@@ -71,7 +71,7 @@ public function __construct(
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public function getThemeByFullPath($fullPath)
     {
@@ -100,7 +100,7 @@ public function getThemeByFullPath($fullPath)
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public function getThemeCustomizations(
         $area = \Magento\Framework\App\Area::AREA_FRONTEND,
@@ -113,11 +113,7 @@ public function getThemeCustomizations(
     }
 
     /**
-     * Get theme by id
-     *
-     * Checks local object cache first, application cache second, and will fall back on creating and loading
-     * a new Theme object. Loaded Theme is only cached by ID, as virtual themes may have matching base paths.
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public function getThemeById($themeId)
     {
@@ -132,6 +128,7 @@ public function getThemeById($themeId)
         $theme = $this->themeFactory->create();
         $theme->load($themeId);
         if ($theme->getId()) {
+            // We only cache by ID, as virtual themes may share the same path
             $this->saveThemeToCache($theme, 'theme-by-id-' . $themeId);
             $this->themes[$themeId] = $theme;
         }

app/code/Magento/Theme/Test/Unit/Model/Theme/ThemeProviderTest.php

@@ -112,10 +112,16 @@ public function testGetByFullPath()
             ]);
         \Magento\Framework\App\ObjectManager::setInstance($objectManagerMock);
 
-        // Assertion for first time load
-        $this->assertSame($this->theme, $this->themeProvider->getThemeByFullPath(self::THEME_PATH));
-        // Assertion for loading from local cache
-        $this->assertSame($this->theme, $this->themeProvider->getThemeByFullPath(self::THEME_PATH));
+        $this->assertSame(
+            $this->theme,
+            $this->themeProvider->getThemeByFullPath(self::THEME_PATH),
+            'Unable to load Theme'
+        );
+        $this->assertSame(
+            $this->theme,
+            $this->themeProvider->getThemeByFullPath(self::THEME_PATH),
+            'Unable to load Theme from object cache'
+        );
     }
 
     public function testGetByFullPathWithCache()
@@ -155,10 +161,16 @@ public function testGetByFullPathWithCache()
             ->with('theme' . self::THEME_PATH)
             ->willReturn($serializedTheme);
 
-        // Assertion for load from cache
-        $this->assertSame($this->theme, $this->themeProvider->getThemeByFullPath(self::THEME_PATH));
-        // Assertion for load from object cache
-        $this->assertSame($this->theme, $this->themeProvider->getThemeByFullPath(self::THEME_PATH));
+        $this->assertSame(
+            $this->theme,
+            $this->themeProvider->getThemeByFullPath(self::THEME_PATH),
+            'Unable to load Theme from application cache'
+        );
+        $this->assertSame(
+            $this->theme,
+            $this->themeProvider->getThemeByFullPath(self::THEME_PATH),
+            'Unable to load Theme from object cache'
+        );
     }
 
     public function testGetById()
@@ -185,10 +197,16 @@ public function testGetById()
             ->with($themeArray)
             ->willReturn('{"theme_data":"theme_data"}');
 
-        // Assertion for initial load
-        $this->assertSame($this->theme, $this->themeProvider->getThemeById(self::THEME_ID));
-        // Assertion for load from object cache
-        $this->assertSame($this->theme, $this->themeProvider->getThemeById(self::THEME_ID));
+        $this->assertSame(
+            $this->theme,
+            $this->themeProvider->getThemeById(self::THEME_ID),
+            'Unable to load Theme'
+        );
+        $this->assertSame(
+            $this->theme,
+            $this->themeProvider->getThemeById(self::THEME_ID),
+            'Unable to load Theme from object cache'
+        );
     }
 
     public function testGetByIdWithCache()
@@ -211,10 +229,16 @@ public function testGetByIdWithCache()
             ->method('create')
             ->willReturn($this->theme);
 
-        // Assertion for initial load from cache
-        $this->assertSame($this->theme, $this->themeProvider->getThemeById(self::THEME_ID));
-        // Assertion for load from object cache
-        $this->assertSame($this->theme, $this->themeProvider->getThemeById(self::THEME_ID));
+        $this->assertSame(
+            $this->theme,
+            $this->themeProvider->getThemeById(self::THEME_ID),
+            'Unable to load Theme from application cache'
+        );
+        $this->assertSame(
+            $this->theme,
+            $this->themeProvider->getThemeById(self::THEME_ID),
+            'Unable to load Theme from object cache'
+        );
     }
 
     public function testGetThemeCustomizations()